R
- RAM
- See random-access memory (RAM).
- random-access memory (RAM)
- Semiconductor-based memory for temporary storage. See also
read-only memory (ROM).
- RARP
- See Reverse Address Resolution Protocol.
- raw device
- In UNIX-based operating systems: A block device that handles data as
a stream of bytes, rather than as a block. Programs such as fsck and
volcopy use disk and tape drives as raw devices.
- RDBMS
- See relational database management system
(RDBMS).
- read-only memory (ROM)
- Semiconductor-based memory for permanent storage. See also
random-access memory (RAM).
- read permission
- In UNIX-based operating systems: On a directory, the ability to list
contents (as with the ls command). On a file, the ability to read
contents (as with the cat command). See also write permission.
- read queue
- In UNIX-based operating systems: The queue in a module or driver
containing messages moving upstream. The read queue is associated with a
read(2) system call and input from a driver.
- reboot
- To start a computer system after a shutdown or halt. This procedure
reinitializes the state of the operating system.
- receiver
- An electronic circuit that converts a signal from the media (optical
or electrical) to an electrical retimed serial logic signal.
- record
-
- A collection of data handled together in transfers to and from
peripheral devices. The collection of data transferred as a unit is called a
"physical record." The collection of data related to one subject is called a
"logical record." See also record length.
- A data structure made up of fields, each with its own name and
type. The elements of a record are accessed by name.
- record length
- The number of bytes or words in a record. See also record.
- recursive
- In programming: Descriptive of a self-invoking function (that is, a
function that contains a reference to itself).
- recycle
- In ptx/SVM: To reinitialize a volume without changing its volume
name. Recycling removes all entries for that volume from the file and media
indexes.
- redirection
- The process of changing either the source for command input or the
destination for command output.
- refresh
- (n) The process of repeatedly producing an image on a display so that
the image remains visible.
(v) To update a visual image on a display or (by extension) a
program image in system memory.
- Registered Private Operating Agency
(RPOA)
- In X.25 networking: A category of routing information in the X.25
packet-switched networking standard. It identifies the telecommunications
service supplier that provides a particular subnet on an X.25 network.
- regular expression
- In UNIX-based operating systems: A pattern used by programs such as
ed, vi, grep, more, and pg to locate
specific character strings in a file. A regular expression can contain special
characters that match groups or ranges of characters.
- relational database management system (RDBMS)
- A software package for the storage and control of logically related
data. The data is stored in structures that facilitate the definition and
manipulation of references among entries.
- relative pathname
- See pathname.
- relay
- In local area networking: A generic term for the equipment that
connects separate local-area networks (LANs). See also
local-area network (LAN).
- reliable transfer service (RTS)
- Under Construction.
- reliable transfer service element
(RTSE)
- Under Construction.
- remote access
- In computer networking: Communication with a data-processing facility
by means of a data link.
- remote job entry (RJE)
- In IBM's Binary Synchronous Communications (BSC) architecture: A
batch-oriented rather than interactive mode of computing over a network. In an
RJE environment, jobs are submitted to a remote host computer, and output is
received later.
- remote login
- The service that allows users on one system to log in to another
system on the network and interact with the remote system as if their terminals
were directly connected to it.
- remote method invocation (RMI)
- A communication protocol that enables the creation of distributed
Java-to-Java applications, in which the methods of remote Java objects can be
invoked from other Java virtual machines, possibly on different hosts. A method
invocation on a remote object has the same syntax as a method invocation on a
local object.
- remote operation
- An action invoked by one application entity but performed by another.
- remote-operations service element
(ROSE)
- In OSI networking: The remote procedure call (RPC) mechanism used by
various OSI network application protocols. See also remote
procedure call (RPC).
- remote procedure call (RPC)
- A high-level mechanism that enables programs on networked platforms
to communicate with local or remote resources.
- repeater
- In local area networking (LAN): A device that copies signals from one
station to another.
- repertoire
- A character set required by computer-to-computer communication; for
example, ASCII or EBSIDIC.
- repertoire assignment
- A method for two computers to agree, at connection, upon a common
character set; for example, ASCII or EBSIDIC.
- request primitive
- The primitive passed from the DLS (data link service) user to the DLS
provider to request that a service be initiated. See also data link service
(DLS).
- request/response header (RH)
- In SNA networking: Control information preceding a request/response
unit (RU), specifying the type of RU (request unit or response unit) and
containing control information associated with that RU. See also request/response unit (RU).
- request/response unit (RU)
- In SNA networking: A request or response unit. A request unit may
contain control information (such as a request code); it may instead contain
function-management (FM) headers, end-user data, or both. A response unit
acknowledges a request unit; it may contain prefix information received in a
request unit. A positive response unit may contain additional information (such
as session parameters in response to BIND SESSION); a negative response unit
contains "sense data" defining the exception condition.
- Request to Send (RTS)
- A signal sent by the data terminal equipment (DTE) to the data
communications equipment (DCE), notifying it that the DTE has data to transmit.
See also data communications equipment (DCE), data terminal equipment (DTE).
- Request for Comments (RFC)
- A series of numbered Internet informational documents and standards
widely followed by commercial software and freeware in the Internet and UNIX
communities. Few RFCs are standards, but all Internet standards are recorded in
RFCs.
- reservation
- In ptx/EFS: An extent attribute that specifies how much space is
preallocated for a file. See also preallocation.
- reserved port
- See well-known port.
- resilvering
- How ptx/SVM makes data on new plexes that are being added to a
volume consistent with other existing plexes already attached to the volume.
- resource
-
- Any facility of the computing system or operating system required
by a job or task; includes main storage, input/output devices, the processing
unit, data sets, and control or processing programs.
- In ptx/XWM: Application options that specify such attributes as
color, font, and behavior. Resources can be set on the command line when a
client application is started, or specified in a resources file (usually
.Xdefaults in the user's home directory). In the latter case, they are read by
clients at start-up, and may also be loaded and stored in the display server
program. Also called ''X resources'' and ''X defaults.''
- resource domain
- One or more FC-connected storage subsystems and the fabric or fabrics
common to them. Resource domains can have single or dual fabrics.
- resource manager
- An interface and associated software providing application access to
a system resource, such as a line printer or a DBMS.
- respawn
- In UNIX-based operating systems: To continuously restart a process
after it has exited. This method is used to make TTY lines available for logins
after users have logged out.
- responder
- The process which enables a host system to communicate with one or
more initiators. In Fibre Channel technology: A Fibre
Channel logical function in an N_port responsible for supporting the exchange
initiated by the originator in another N_port. See also
N_port, originator.
- response primitive
- In OSI networking: The primitive passed from the data link service
(DLS) provider to the DLS user to acknowledge reception of a previous
indication and to convey the desired action of the DLS provider in reponse to
the previous indication. See also data link service (DLS) provider, data link
service (DLS) user.
- restore
- To recover files, directories, or filesystems from a backup medium.
- resynchronization
- How ptx/SVM keeps data on mirrored plexes consistent.
Resynchronization is the process by which ptx/SVM updates an already-attached
plex that may contain valid, but slightly out-of-date, data.
- Reverse Address Resolution Protocol (RARP)
- In TCP/IP networking: A protocol by which a diskless machine can
obtain its IPaddress from a RARP server. The diskless machine broadcasts a
request and its physical hardware address. The RARP server responds by
returning an IP address based on the physical address. See also
BOOTstrap Protocol.
- revision text
- See version identifier.
- RFC
- See Request for Comments.
- RH
- See request/response header.
- RIP
- See Routing Information Protocol.
- RJE
- See remote job entry (RJE).
- RMI
- See remote method invocation
- RMS
- See VMS Record Management System (RMS).
- Rock Ridge Interchange Protocol (RRIP)
- An extension of the ISO-9660 format for CD-ROM that provides support
for POSIX filesystem semantics, including UNIX-style filenames, file types,
file permissions, and directory hierarchies.
- rolling upgrade
- In clustered systems: Updating the system software on a cluster
without interrupting service to the users of the cluster.
- ROM
- See read-only memory (ROM).
- root
- In UNIX-based operating systems: The account name of the superuser,
who has access to all files and directories and is the owner of most system
files.
- root device
- In UNIX-based operating systems: The disk drive on which the root
partition resides.
- root directory
- In UNIX-based operating systems: The source of the filesystem,
represented by a slash (/).
- root filesystem
- In UNIX-based operating systems: The first filesystem in the
operating system. It begins with the root directory and contains several system
directories as well as the operating system kernel.
- root login
- See root.
- root partition
- In UNIX-based operating systems: The disk partition that contains the
root filesystem.
- ROSE
- See remote-operations service element
(ROSE).
- rotational delay
- In data-storage hardware: The time it takes a disk to rotate so that,
once the disk drive has moved the head, the data is under the head and over the
right track.
- round-robin
- Describing an activity that occurs in a set, cyclic order among a
group of devices or programs. For example, bus access is granted to Symmetry
system boards on a round-robin basis (within a high- or low-priority group).
- route
- The path that network traffic takes from the source to the
destination.
- router
- A relay that stores and forwards data packets directly addressed to
it by user systems. The router and the source and destination systems must all
adhere to a common routing protocol.
- Routing Information Protocol (RIP)
- A protocol used to exchange routing information among systems on a
small network. The protocol is implemented through a daemon called
routed.
- RPC
- See remote procedure call (RPC).
- RPOA
- See Registered Private Operating Agency
(RPOA).
- RRIP
- See Rock Ridge Interchange Protocol (RRIP).
- RS-232-C
- A 25-wire electrical interface for serial communication between a
computer and a peripheral device; defined by EIA Standard RS-232.
- RTS
-
- See Request to Send (RTS).
- See reliable transfer service (RTS).
- RTSE
- See reliable transfer service element
(RTSE).
- RU
- See request/response unit (RU).
- run queue
- In DYNIX/ptx, one or more CPUs that execute assigned processes in
accordance with the priority and attributes specified by the system
administrator.
- run level
- In the DYNIX/ptx operating system: one of several states of the
computer system, each appropriate for different sets of operational or
maintenance activities, such as single-user mode or multiple-user mode.
- run limit
- The maximum number of jobs that can execute simultaneously. Run
limits apply to batch and pipe queues, batch queue complexes, and globally to
all batch jobs. These limits are set by the system administrator.
- run time
- The time during which a program is running.
S
- SA
- See system administrator.
- SAK
- See stand-alone kernel.
- SAP
- See service access point.
- SAR
- See segmentation and reassembly (SAR).
- Scalable Coherent Interconnect (SCI)
- Standard for internal processor-memory connections within computers,
based on the IEEE standard for Scalable Coherent Interface (SCI), IEEE Std
1596-1992. A variant is used to implement cache coherence in IBM NUMA systems.
SCI-connected processors do not have to use I/O operations to communicate; they
can use ordinary load and store instructions to directly access one another's
memory.
- Scan Interface Controller (SIC)
- An application-specific integrated circuit (ASIC) for controlling
scan and clock functions. See also application-specific integrated circuit
(ASIC).
- SCB
- See string control byte (SCB).
- SCC
- See Synchronous Communications Controller
(SCC).
- SC-style connector
- In IBM NUMA hardware: A rectangular, keyed connector that houses the
end of an optical fiber. The connector mates to the receptacle of a Gigabaud
Link Module (GLM) Gigabit Interface Converter, or Gigabit Optical Transceiver.
SC stands for Subscriber Connector. It has different configurations depending
on whether the optical devices and cables are multimode or single mode.. See
also Gigabaud Link Module,
Gigabit Interface Converter, and
Gigabit Optical Transceiver.
- SCC-V
- See Synchronous Communications Controller - VMEbus
(SCC-V).
- SCED Board
- See SCSI/Ethernet/Diagnostics (SCED)
Board.
- schedule
- In STREAMS programming: To place a queue on the internal list of
queues that will subsequently have their service procedure called by the
STREAMS scheduler.
- SCI
- See Scalable Coherent Interconnect.
- SCI Cache Link Interface Controller (SCLIC )
- An application-specific integrated circuit (ASIC) that connects the
SCI to the IQ-Link board in each node. See also application-specific integrated circuit (ASIC),
Scalable Coherent Interface (SCI).
- SCS
- See Systems Network Architecture (SNA) character
string.
- SC-style connector
- In IBM NUMA hardware: A rectangular, keyed connector that houses the
end of an optical fiber. The connector mates to a receptacle of a
gigabaud link module (GLM).
- SCSI
- See Small Computer Systems Interface (SCSI).
- SCSI disk
- A 3.5-inch or 5.25-inch fixed-media device with an integrated
controller which connects to the SCSI bus.
- SCSI/Ethernet/Diagnostics (SCED)
Board
- A circuit board required in the S27, S81, and S2000/400, and optional
in the Symmetry 2000/700. The SCED provides S27 and S81 systems with system
initialization, bus services, diagnostic control, power-supply monitoring, and
battery-backed clock. The SCED includes an asynchronous SCSI bus, an Ethernet
port, and two serial ports. The SCED may be used in S2000/400 and S2000/700
systems to provide an Ethernet interface. See also Small
Computer Systems Interface (SCSI).
- SCSI Expansion Cabinet (SEC)
- In S2000 systems hardware: A small expansion cabinet used with the
SCSI-V board to provide more disk drives for the S16 and S2000/2x0 systems. See
also Small Computer Systems Interface (SCSI).
- SCSI Peripheral Bay
- See Pbay.
- SCSI/Processor Interconnect (SPI)
- An integrated circuit used in SCSI controller boards. The SPI is used
to control the access of the controller board's local processor to memory on
the Symmetry System bus, and of system CPUs to the controller board's local
memory. See also SCSI/Processor Interconnect, Fast (SPIF)
Small Computer Systems Interface (SCSI).
- SCSI/Processor Interconnect, Fast (SPIF)
- An enhanced version of the SCSI/Processor Interconnect the SPIF is
used in systems based on the Highly Scalable bus.) See also SCSI/Processor Interconnect (SPI), Small
Computer Systems Interface (SCSI).
- SCSI-V board
- In older Symmetry systems: A VMEbus board that provides an S16 or
S2000/2x0 system with two additional SCSI buses for disk drives.
- SDH
- See Synchronous Digital Hierarchy (SDH).
- SDLC
- See synchronous data link control (SDLC).
- SEAL
- See simple and efficient AAL (SEAL).
- search path
- A list of directories searched by the shell when a command pathname
is not specified. See also pathname.
- SEC
- See SCSI Expansion Cabinet
- secondary half-session
- In SNA networking: The half-session that receives the
session-activation request. See also primary half-session.
- secondary logical unit (SLU)
- In SNA networking: The logical unit that receives the Bind Session
(BIND) request for a particular logical unit-to-logical unit (LU-to-LU)
session. See also logical unit (LU),
primary logical unit (PLU).
- security descriptor
- In Windows NT: Security-related information associated with every
object in the Windows NT operating system. The main feature of a security
descriptor is a list of protections, called the access control list (ACL), that
apply to the object.
- security identifier (SID)
- In Windows NT: A string that uniquely identifies the user to the NT
operating system's security functions. Usually corresponding to the user's
login name, it may also incorporate the name of a group to which the user
belongs. The SID is one of the components of an access token. See also
access token.
- segmentation and reassembly (SAR)
- In OSI networking: One of the two sublayers of the Asynchronous
Tranfer Mode (ATM) Adaptation Layer (AAL) common part convergence sublayer
(CPCS) responsible for dividing (at the source) and reassembling (at the
destination) the protocol data units (PDUs) passed from the convergence
sublayer (CS). The SAR sublayer takes the PDUs processed by the CS and, after
dividing them into 48-byte pieces of user data, passes them to the ATM layer
for further processing. See also Asynchronous
Tranfer Mode (ATM), ATM Adaptation Layer
(AAL), common part convergence sublayer
(CPCS), convergence sublayer (CS),
protocol data unit (PDU).
- select window
- In ptx/ADMIN: A window that allows the user to select one or more
items for entry into a field.
- selector
- In OSI networking: The portion of an address that identifies a
particular entity at that address; for example, a session selector identifies a
user of the session service residing at a particular address.
- semaphore
- In programming: A shared data structure used to synchronize the
actions of multiple cooperating processes.
- semopset
- In programming: A collection of semaphore-controlled operations that
work as one operation. If some event prevents completion of the semopset, any
operations that have been performed are undone.
- Sendmail
- In UNIX-based operating systems: A program that controls mail routing
and address parsing.
- sequential execution
-
- The execution of multiple commands typed on the same line. The
commands, separated by semicolons, execute in the order in which they appear on
the line.
- The processing of computer instructions one after another; as
opposed to parallel execution. See also parallel execution.
- server
- The program satisfying the request in a system in which a program at
one site sends a request to a program at another site. See also
host(2), display server.
- service access point (SAP)
- In OSI networking: The point at which a communications protocol layer
receives services from the underlying layer.
- service data unit (SDU)
- In OSI networking: A unit of information from an upper-layer protocol
that defines a service request to a lower-layer protocol.
- service interface
- In network programming for UNIX-based systems: A specified set of
messages and the rules for allowable sequences of messages across the boundary
of neighboring components within a stream.
- service procedure
- In network programming for UNIX-based systems: The queue routine that
receives a message from the queue's message list, processes it, and passes it
to the following queue's put procedure. The STREAMS scheduler calls the service
procedure.
- service provider
- In a service interface: The entity (typically a module or driver)
that responds to request primitives from the service user with response and
event primitives.
- service user
- In networking: The entity that generates request primitives for the
service provider and consumes response and event primitives.
- session
- In SNA networking: A logical or virtual path established between two
network addressable units (NAUs) for the purpose of exchanging data. See also
network addressable unit (NAU).
- session layer
- In OSI networking: The layer that adds control mechanisms to the data
exchange; often called ''layer 5.'' See also Open
System Interconnection (OSI) reference model.
- session limit
- In SNA networking: The flow-control technique that permits a
receiving session to control the data transfer rate (the rate at which it
receives request units) on the normal flow. It is used to prevent overloading a
receiver with unprocessed requests when the sender can generate requests faster
than the receiver can process them. See also pacing.
- session partner
- In SNA networking: One of the two network addressable units (NAUs)
engaged in an active session. See also network
addressable unit (NAU).
- session presentation services
- In SNA networking: The component of the FMD services layer that
provides, within a logical unit-to-logical unit (LU-to-LU) session, services
(such as formatting data for display or printing) to the application programmer
or terminal operator. See also logical unit
(LU).
- session services
- In SNA networking: One of the types of network services in the system
services control point (SSCP) and in a logical unit (LU). These services
provide facilities for a logical unit (LU) or network operator to request that
the SSCP initiate or terminate sessions between logical units. See also
logical unit (LU), system
services control point (SSCP).
- session services access point (SSAP)
- Under Construction.
- set-associative cache
- A cache-memory architecture that divides the cache memory into banks
or "ways" the same size as a memory page.
- shared-memory multiprocessor
- A type of computer system in which all processors share a single
memory system. The processors in such a system are able to cooperate with one
another and balance the workload among themselves by passing data back and
forth through the shared memory system. This type of design is called
"tightly-coupled."
- shell
- A program responsible for handling all interaction between the user
and the operating system. Shells include a limited programming language with
which shell scripts can be written. See also shell
script.
- shell script
- A file containing commands that can be interpreted by the shell. The
user types the name of the script file at the shell command prompt to make the
shell execute the script commands.
- shut down
- To halt or stop a computer system.
- SIC
- See Scan Interface Controller (SIC).
- SID
- See security identifier (SID).
SilkWorm
"SilkWorm" refers to the first generation 16-port Fibre Channel Switch.
"SilkWorm Express" refers to the first generation 6-port switch. (our special
model is 6-port; Brocade's standard model is 8-port.) "SilkWorm 2800" is the
term for the second generation 16-port switch. "SilkWorm 2400" is the name for
the second generation 8-port switch.
The "SilkWorm 2000 family of switches" or the "SilkWorm 2000 family" are
terms that refer to the newer switch models (SilkWorm 2800 and SilkWorm 2400).
"SilkWorm 1000 family" refers to the older generation of switches, which
included the 16-portSilkWorm and the 6-port SilkWorm Express (see above).
- simple and efficient AAL (SEAL)
- In OSI networking: A scheme used by ATM Adaptation Layer 5 (AAL5), in
which the segmentation and reassembly (SAR) sublayer segments convergence
sublayer (CS) protocol data units (PDUs) without adding additional fields. See
also ATM Adaptation Layer (AAL),
convergence sublayer (CS),
protocol data unit (PDU), segmentation and reassembly (SAR).
- simple disk
- An unpartitioned ptx/SVM disk that contains a small area for private
configuration database and header information, and a large public area that
ptx/SVM uses for subdisk storage.
- Simple Mail-Transfer Protocol (SMTP)
- An Internet protocol providing electronic mail services.
- Simple Network-Management Protocol
(SNMP)
- In computer networking: A protocol used to monitor IP gateways and
the networks to which a gateway is attached. SNMP defines a set of variables to
be stored on each gateway in the Management Information Base (MIB) database. An
SNMP agent on the gateway keeps track of variables and responds to SNMP
requests. An SNMP manager resides on a system on the network and sends out
requests for network information from SNMP agents. The information returned by
the agents is processed by the manager and displayed on the manager's system.
See also Management Information Base.
- single inline memory module (SIMM)
- In computer hardware: A small circuit card that carries a number of
surface-mounted memory chips in a space-saving configuration with the connector
pins protruding in a single line from the edge of the card. Varying numbers of
SIMMs can be plugged easily into slots in a memory board to expand
random-access memory.
- single-mode fiber
- A type of optical fiber, typically used with Gigabaud Link Modules
(GLMs) incorporating longwave lasers. Typically used for long-distance links up
to 10 km. See also Gigabaud Link Module
(GLM).
- single-mode optical transmission
- In fiber-optical transmission: The propagation of light on a single
path through an optical fiber of small core diameter. The single path allows
transmissions up to 10 km.
- single-user mode
- In UNIX-based operating systems: A state of the computer that allows
only the superuser to gain access to the operating system.
- site
- A place where one or more computer systems are installed. To operate
properly over their intended service life, computer systems typically require
certain site conditions, such as a stable electrical power supply and adequate
circulation of clean, cool air around the system.
- site license
- Authorization to use a software product on all computers at a
site.
- slave system
- In UNIX networking: A system that receives a UNIX-to-UNIX copy (UUCP)
call. See also UNIX-to-UNIX copy (UUCP).
- SLIC
- See System-Level Interrupt Controller
(SLIC).
- SLIC bus
- See System-Level Interrupt Controller (SLIC)
bus.
- slice
- See partition.
- sliced disk
- A ptx/SVM disk that consists of one type-8 partition designated to
contain the configuration database and one non-type-3, type-8, or type-9
partition for data.
- SLU
- See secondary logical unit (SLU).
- Small Computer Systems Interface
(SCSI)
- A family of hardware interfaces based on the ANSI X3.131-1986
standard which are used to connect peripherals such as disk and tape drives to
computer systems. Derivatives of the original single-ended narrow SCSI bus
(SCSI-1) include Differential SCSI, Wide Differential SCSI, and Fast Wide
Differential SCSI.
- SMD-E
- See Storage Module Disk - Extended (SMD-E).
- SMT
- See surface-mount technology (SMT).
- SMTP
- See Simple Mail-Transfer Protocol (SMTP).
- SNA character string (SCS)
- See Systems Network Architecture (SNA) character
string (SCS).
- SNA network
- A data communications network employing IBM's Systems Network
Architecture. See Systems Network Architecture (SNA).
- SNDCF
- See Subnetwork-Dependent Convergence Facility
(SNDCF).
- SNMP
- See Simple Network-Management Protocol (SNMP)
.
- snode
- The filesystem-specific node that underlies Virtual File System (VFS)
vnodes for device-special files, FIFO files, and pipe files. See also
Virtual File System (VFS), vnode.
- SNPA
- See subnetwork point of attachment (SNPA).
- socket
- In TCP/IP networking: A software interface that gives an application
program access to the TCP/IP services. An alternative to the Transport Layer
Interface. See also Transport Layer Interface (TLI).
- space files
- Files that contain configurable source code for device drivers or
that list system configuration parameters. These files are called space files
because they specify the space requirements for the kernel. The total space
requirements will affect the amount of memory used by the kernel.
- spawn
- To create a process; for example, at boot time, the init
process spawns a getty process for each TTY port that can accept logins.
- special character
- A character that instructs the shell to perform a task such as
redirecting input or output, or matching filenames on the command line.
- special file
- A file that represents a physical device such as a printer, terminal,
or disk drive. When the system reads from and writes to these files, the read
and write requests activate the device handler associated with the file.
- SPI
- See SCSI/Processor Interconnect (SPI).
- SPIF
- See SCSI/Processor Interconnect (SPI), Fast
(SPIF).
- split transaction
- A concept used on the Symmetry System Bus (SSB) and Highly Scalable
Bus (HSB), in which a read or write transaction on the bus need not take place
during contiguous bus cycles. See also Symmetry System Bus
(SSB), Highly Scalable Bus (HSB).
- spool
- In UNIX-based operating systems: To queue a job for completion in the
background. Print requests and UUCP jobs are spooled.
- SSAP
- See session services access point (SSAP).
- SSB
- See Symmetry System Bus (SSB).
- SSCP
- See system services control point (SSCP).
- SSCP services
- In SNA networking: The components in a system services control point
(SSCP) that provide configuration, maintenance, management, network, and
session services for SSCP-to-LU, SSCP-to-PU, and SSCP-to-SSCP sessions. See
also Logical Unit (LU),
Physical Unit (PU), system services control
point (SSCP).
- SSCP-to-LU session
- In SNA networking: A session between a system service control point
(SSCP) and a logical unit (LU); the session enables the LU to request the SSCP
to help initiate LU-to-LU sessions. See also Logical
Unit (LU), Physical Unit (PU),
system services control point (SSCP).
- SSCP-to-PU Session
- In SNA networking: A session between a system services control point
(SSCP) and a physical unit (PU); SSCP-to-PU sessions allow SSCPs to send
requests to, and receive status information from, individual nodes to control
the network configuration. See also Physical Unit
(PU), system services control point
(SSCP).
- SSCP-to-SSCP session
- In SNA networking: A session between the system service control point
(SSCP) in one domain and the SSCP in another domain. An SSCP-to-SSCP session is
used to initiate and terminate cross-domain logical unit-to-logical unit
(LU-to-LU) sessions. See also Logical Unit (LU),
system services control point (SSCP).
- SSM
- See System Services Module (SSM).
- SSM-2
- See System Services Module - 2 (SSM-2).
- stand-alone kernel
- In IBM NUMA systems, a subset of the UNIX kernel that lives in the
flash PROM of the Management and Diagnostics Controller (MDC). It includes only
those modules necessary for a stand-alone environment and does not provide a
swap device. The stand-alone kernel reads the boot strings from the MDC and
loads the UNIX-kernel or stand-alone utility specified by the boot strings.
- stand-alone program
- In computer operating systems: A program that can be used when the
operating system is not running.
- star topology
- In network architecture: A network topology in which every node on
the network is connected to a central node or "hub," through which they
communicate with each other.
- station
- In OSI network architecture: A uniquely addressed network device.
Stations implement the services defined by the Data Link and Physical layers of
the OSI reference model. See also Open Systems
Interconnection (OSI) reference model.
- statistical multiplexing
- Technique whereby information from multiple logical channels can be
transmitted across a single physical channel. Statistical multiplexing
dynamically allocates bandwidth only to activate input channels. This makes
better use of available bandwidth and allows more devices to be connected than
with other multiplexing techniques.
- STM-1
- See Synchronous Transport Module level 1
(STM-1).
- Storage Module Disk - Extended (SMD-E)
- An industry-standard disk-drive interface.
- stream
- In the DYNIX/ptx operating system: A full-duplex processing and
data-transfer path between a STREAMS driver in kernel space and a process in
user space. A stream is created using the STREAMS mechanism. The primary
components of a stream are the stream head, the driver, and zero or more
modules between the stream head and driver. See also STREAMS.
- stream end
-
In the DYNIX/ptx operating system: The module farthest from the user
process, in which the processing procedures are driver routines. A stream-end's
procedures are different from those in other modules because they are
accessible from an external device and because the STREAMS mechanism allows
multiple streams to be connected to the same driver (the same stream end).
The terms stream end and driver are often used
interchangeably.
- stream entity
- In the DYNIX/ptx operating system: Any one of the elements of which a
stream is made: a driver, module, multiplexor, or stream head.
- stream head
- In the DYNIX/ptx operating system:The end of the stream closest to
the user process. The stream head provides the interface between the stream and
the user process. Its principal functions are processing of STREAMS-related
system calls and bidirectional transfer of data between a user process and
messages in the STREAMS kernel space.
- STREAMS
- In the DYNIX/ptx operating system: The set of utility routines,
kernel facilities, and structures that define interface standards for character
input and output.
- string
- A series of characters.
- string control byte (SCB)
- In SNA networking: An optional control byte in the SCS data stream
that identifies how end-user data is compressed or compacted. See also
compaction,
compression.
- striping
- In ptx/SVM: A type of plex layout where data blocks are interleaved
between subdisks. Data is written alternately to a portion, or stripe, of each
subdisk on multiple disks.
- STS-1
- See Synchronous Transport Signal level 1
(STS-1).
- subarea
- The combination of a host or communication controller and its
attached peripheral nodes.
- subdirectory
- In computer operating systems: A directory located "below" another
directory in the filesystem. Also called a child directory.
- subdisk
- In ptx/SVM: The smallest logical building block of ptx/SVM. A subdisk
is mapped directly to part or all of a single physical disk partition. Subdisks
make up plexes, which make up ptx/SVM volumes. See also
plex, volume.
- submenu
- In computer user interfaces: A menu that appears as an option on
another menu.
- subnet addressing
- See subnetting.
- subnet mask
- See netmask.
- subnetting
- The "Internet Standard Subnetting Procedure" is specified in RFC 950.
Also known as "subnet addressing," subnetting is a widely used technique that
allows a single network address to be divided into multiple logical networks,
each of which forms a subset of the total network address space. Subnetting is
now a required extension of the IP addressing scheme.
The advantage of subnetting is that it allows partitioning of the
network address space within an organization without affecting the way senders
outside the organization address messages sent to it. The internal organization
is wholely contained within the organization.
See also
netmask.
- subnetwork
- A logical subsection of a network. Sometimes called ''subnet.'' See
also subnetting.
- Subnetwork-Dependent Convergence Facility
(SNDCF)
- Under Construction.. (ISO 8473 and 9068).
- subnetwork point of attachment (SNPA)
- Under Construction.
- suffix
- See filename
extension.
- superblock
- In UNIX-based operating systems: A block containing critical
information about the filesystem, such as the filesystem type, layout, and
size. The ptx/EFS superblock is located 1024 bytes from the beginning of the
filesystem and is 1024 B long.
- superuser
- In UNIX-based operating systems: Owner of most system files and user
of the root login name. The superuser has access to every file, regardless of
its permission levels. Most system administration tasks are performed by the
superuser under the root login name.
- surface-mount technology (SMT)
- A method for manufacturing printed circuit boards in which chips are
fixed directly to the surface of the board instead of being soldered into
predrilled holes.
- SVC
- See switched virtual circuit (SVC).
- SVID
- See System V Interface Definition (SVID).
- SVR4
- UNIX System V Release 4.
- svsema
- See System V semaphore (svsema).
- swap device
- A reserved set of disk partitions that store processes temporarily.
When there is not enough primary memory to contain all the processes that are
running, the kernel writes processes to a swap device. Later, the kernel reads
the data from the swap device back into primary memory.
- swap partition
- See swap space.
- swap space
- Disk space reserved to hold processes that are swapped out of primary
memory.
- switched line
- A telecommunication line in which the connection is established by
dialing. See also dedicated line.
- Switched Multimegabit Data Service
(SMDS)
- Wide-area network technology featuring high-speed packet switching of
datagrams.
- switched virtual circuit (SVC)
- In data-communications networking: A virtual circuit that is
dynamically established on demand and is torn down when transmission is
complete. SVCs are used in situations where data transmission is sporadic. In
Asynchronous Tranfer Mode (ATM) networking: "switched virtuial connection."
Compare with permanent virtual circuit
(PVC). See also Asynchronous Tranfer Mode
(ATM).
- symbolic address
- In UNIX-based operating systems: A character representing a specific
line in a text file. Used by the ed and vi editors.
- symmetric multiprocessing
- A system in which all CPUs are identical, and any CPU can execute
both user code and kernel code. In the Symmetry system architecture, all CPUs
operate on a peer basis, executing a single copy of the operating system
executive or kernel. There is no designated master CPU except during system
start-up and diagnostic operations. Any process (program) in any state can
execute on any CPU.
- Symmetry 2000 systems
- A family of computers, now obsolete, built around the Symmetry System
Bus (SSB) architecture. See also Symmetry System Bus
(SSB).
- Symmetry 5000 systems
- The family of computers running the DYNIX/ptx operating system and
using the Highly Scalable Bus (HSB). A collective term for the SE20, SE30,
SE40, SE60, SE70, and SE80 computer systems. See also
Highly Scalable Bus (HSB).
- Symmetry System Bus (SSB)
- A 64-bit bus that links the S2000 systems' CPUs, memory, and I/O
subsystems. Peripheral interface boards connected to the SSB allow the CPUs to
access mass-storage devices, printers, and other peripherals that are connected
to the Small Computer Systems Interface (SCSI) bus and the VMEbus or MULTIBUS.
Processor boards, Memory Controller boards, Memory Expansion boards, bus
adapter boards, and peripheral controller boards are installed in the system
backplane and connect to the system bus. The specific boards and the number of
each that can be installed depend on the system. See also MULTIBUS, Small Computer
Systems Interface (SCSI), VMEbus.
- synchronous
- Pertaining to two or more processes that depend upon the occurrence
of specific events, such as common timing signals.
- Synchronous Communications Controller
(SCC)
- A MULTIBUS board providing four high-speed RS-232-C serial interface
ports to support the High-Level Data Link Control (HDLC) data-link protocol for
use in X.25 networks. See also High-Level Data
Link Control (HDLC), MULTIBUS.
- Synchronous Communications Controller - VMEbus
(SCC-V)
- A VMEbus board providing two RS-232-C and two RS-442/449 high-speed
serial interface ports to support the High-Level Data Link Control (HDLC)
data-link protocol for use in X.25 networks. See also
High-Level Data Link Control (HDLC),
VMEbus.
- synchronous data link control (SDLC)
-
- A discipline for managing synchronous, code-transparent,
serial-by-bit information transfer over a link connection. Transmission
exchanges may be duplex or half-duplex over switched or nonswitched links. The
configuration of the link connection may be point-to-point, multipoint, or
loop.
- In SNA networking: The primary data link control protocol. SDLC
transfers data and control and status information.
- Synchronous Digital Hierarchy (SDH)
- European standard that defines a set of rate and format standards
transmitted using optical signals over fiber. STS-1 is similar to Synchronous
Optical Network (SONET) with a basic SDH rate of 155.52 Mbps, designated at
STM-1. See also Synchronous Transport Module level 1
(STM-1), Synchronous Optical Network (SONET).
- Synchronous Optical Network (SONET)
- In OSI networking: High-speed (up to 2.5 Gbps) synchronous network
specification developed by Bellcore and designed to run on optical fiber. STS-1
is the basic building block of SONET. Approved as an international standard.
- Synchronous Transport Module level 1
(STM-1)
- One of a number of SDH formats that specifies that frame structure
for the 155.52-Mbps lines used to carry Asynchronous Tranfer Mode (ATM) cells.
See also Asynchronous Tranfer Mode (ATM),
Synchronous Digital Hierarchy (SDH).
- Synchronous Transport Signal level 1
(STS-1)
- In OSI networking: Basic building block signal of Synchronous Optical
Network (SONET), operating at 51.84 Mbps. Faster SONET
rates are defined as STS-n, where n is a multiple of 51.84
Mbps. See also Synchronous Optical Network (SONET).
- synchronous write
- A form of synchronous I/O that writes the file data to disk, updates
the inode times, and writes the updated inode to disk. When the write returns
to the caller, both the data and the inode have been written to disk.
- syntax
-
- In programming: The rules governing the structure and content of
the statements in a computer language.
- In computer operating systems: The content and structure of the
character strings which, entered at the command line, instruct the operating
system to run a program.
- system
- In IBM NUMA computers: A single or a cluster of nodes acting as a
single computing entity. A system in this sense may run multiple instances of
the operating system. See also cluster,
node.
- System V Interface Definition (SVID)
- In UNIX-based operating systems: An AT&T specification for the
UNIX System V operating system. SVID Release 3 (SVID-III) specifies the
interface for UNIX System V Release 4.
- System V semaphore (svsema)
- In UNIX-based operating systems: A flag for controlling access to
shared memory.
- system administrator (SA)
- A person responsible for the overall operation of the computer
system. The SA's duties include adding and removing user names and devices,
performing configuration tasks, and monitoring system activity.
- system configuration file
- A text file that specifies the modules and device configurations to
be included in the kernel. The default system configuration file is
/etc/conf/uts/symmetry/system.std. This file serves as input to the
config program.
- system default destination printer
- A printer or class that receives print requests that do not include a
destination. If a user has not set the LPDEST variable and does not specify a
destination for a print request on the command line, the print request goes to
the system default destination.
- system directory
- In UNIX-based operating systems: A directory containing files used by
the operating system. Examples include /dev (containing device nodes),
/etc (containing system administration files), and /usr and
/bin (containing programs).
- System-Level Interrupt Controller (SLIC)
- An integrated circuit used to generate and process the signals which
coordinate activity on the Symmetry system bus. Each board connected to the
Symmetry system bus has a SLIC chip. See also System-Level
Interrupt Controller (SLIC) bus.
- System-Level Interrupt Controller (SLIC) bus
- A 1-bit data path in the system backplane that interconnects all the
SLICs in the system. The various subsystems and CPUs in a Symmetry system use
the SLIC bus to exchange interrupts and other low-level control signals,
configuration information, and error information.
- system name
- The name for a system. In a network, this name is typically the same
as the node name.
- system services control point (SSCP)
- In SNA networking:
- A special-purpose network addressable unit (NAU) that controls
and manages resources in a network domain. The SSCP initiates or establishes
communication within the network. See also network
addressable unit (NAU).
- A focal point for managing the configuration, coordinating
network-operator and problem-determination requests, and providing directory
support and other session services for end users of the network. Multiple
SSCPs, cooperating as peers, can divide the network into domains of control,
with each SSCP controlling the physical and logical units in its domain. See
also Systems Network Architecture (SNA) network,
SSCP services.
- System Services Module (SSM)
- A circuit board used in the S16 and Symmetry 2000/200 systems. The
SSM provides these systems with initialization, system-bus services,
power-supply monitoring, and an interface with the front panel. The SSM
includes a differential Small Computer Systems Interface (SCSI) bus, a VMEbus
interface, two serial ports, and a parallel printer port. See also
Small Computer Systems Interface (SCSI),
VMEbus.
- System Services Module - 2 (SSM-2)
- A circuit board used in the Symmetry 2000/4x0 and Symmetry 2000/7x0
systems. The SSM-2 provides these systems with initialization, system-bus
services, power-supply monitoring, and an interface with the front panel. The
SSM-2 includes a differential Small Computer Systems Interface (SCSI) bus and
two serial ports. See also Small Computer Systems Interface
(SCSI), System-Level Interrupt
Controller (SLIC) bus.
- System Services Section
- A functionally distinct portion of the CSM board; it provides
Symmetry 5000 and WinServer 5000 systems with initialization, system-bus
services, power-supply monitoring, and an interface with the front panel. See
also High-Performance SCSI and Ethernet
(HPSE).
- Systems Network Architecture (SNA)
-
- IBM's communications architecture, which permits distributed
processing in a mainframe environment.
- Description of the logical structure, formats, protocols, and
operational sequences for transmitting information units through and
controlling the configuration and operation of networks.
- Systems Network Architecture (SNA) character string
(SCS)
- In SNA networking: A string of EBCDIC control characters carried
within a request/response unit (RU); the string may also contain end-user data.
See also request/response unit (RU),
EBCDIC.
- Systems Network Architecture (SNA) functional
layers
- The division of network services into five layers, as defined in
IBM's Systems Network Architecture. From top to bottom the layers are Function
Management, Data Flow Control, Transmission Control, Path Control, and Data
Link Control. SNA predated the Open Systems Interconnection (OSI) standard's
seven-layer model.
- Systems Network Architecture (SNA) network
- A data communications network employing IBM's Systems Network
Architecture. See Systems Network Architecture (SNA).
T
- T3
- In OSI networking: Digital wide-are network (WAN) carrier facility.
T3 transmits DS-3-formatted data at 44.736 Mbps through the telephone switching
network. Compare with E3.
- tape
- A serial magnetic medium on which data is stored.
- target
- In ptx/LICENSE: The node on which a password is to be installed. If
the password specifies a single nodelocked license, the target is the node
licensed to run the product. If the password specifies multiple nodelocked
licenses (that is, a compound password for nodelocked licenses), or licenses of
any other type, then the target is a node running the license management
daemon.
- target ID
- In ptx/LICENSE: The identifier of the node (in IBM NUMA-Q 2000
systems) or system (in Symmetry systems) on which a password is to be
installed.
- Target System Control Library (TSCL)
- The low-level command layer between system hardware and Virtual
Control Software (VCS). See also Virtual Control Software
(VCS).
- TCAM
- See telecommunications access method (TCAM).
- TCP
- See Transmission Control Protocol (TCP).
- TCP/IP
- See Transmission Control Protocol (TCP),
Internet Protocol (IP).
- TDM
- See time-division multiplexing (TDM).
- Technical Office Protocol (TOP )
- In OSI network architecture: An architecture developed by Boeing for
office communication. See also Open Systems
Interconnection (OSI) reference model.
- Telebit
- A brand of modem.
- telecommunications access method (TCAM)
- A service used by an application program to move data to and from an
I/O device.
- teletypewriter (TTY)
- Originally an electromagnetic device consisting of a combined
keyboard and printer, used to communicate over telephone lines or other wired
serial connections using the ASCII code. The abbreviation TTY is now used to
describe any serial "teletypewriter-like" connection.
- teletypewriter (TTY) line
- An RS-232-C transmission line used for connecting serial devices such
as terminals and printers. See also teletypewriter
(TTY).
- TELNET (TELecommunications NETwork)
- In networking: A standard Internet protocol for terminal
emulation.
- termcap (TERMinal CAPability) file
- Terminal capability database defining a given type of terminal, such
as VT100, network, hp, dialup, and so forth; contains details about each type
of terminal, such as lines-per-screen, columns-per-line, and cursor-control
codes. The word termcap is also used in reference to a line in the file.
- Terminal Line Controller - Multibus
(TLC-M)
- A set of two MULTIBUS boards that provides 16 serial ports for
connecting terminals, modems, and other serially interfaced devices. See also
MULTIBUS.
- Terminal Line Controller - VMEbus
(TLC-V)
- A VMEbus board that provides 16 serial ports for connecting
terminals, modems, and other serially interfaced devices. See also
VMEbus.
- TFTP
- See Trivial File-Transfer Protocol (TFTP).
- throughput
- A measure of work accomplished in a given amount of time. For
filesystems, throughput typically refers to the numbers of I/O operations
performed in a given amount of time.
- tightly coupled multiprocessor
- See shared-memory multiprocessor.
- time-division multiplexing (TDM)
- Techniques in which information from multiple channels can be
allocated bandwidth on a single wire based on preassigned time slots. Bandwidth
is allocated to each channel regardless of whether the station has data to
transmit.
- time stamp
- In ptx/LICENSE: An integer that describes the date and time at which
a set of licenses was created.
- time-sharing option (TSO)
- An optional configuration of IBM's operating system providing
conversational time-sharing from remote stations.
- TLC-M
- See Terminal Line Controller - Multibus
(TLC-M).
- TLC-V
- See Terminal Line Controller - VMEbus
(TLC-V).
- TLI
- See Transport-Layer Interface.
- token
- In networking: A string of bits that passes from one station to the
next on a bus or ring. A station that wishes to transmit a message retrieves
the token and places its message on the medium with the token behind it.
- TOP
- See Technical Office Protocol.
- topology
- In networking: The pattern described by the interconnections among
the nodes in a network. Common topologies include ring, bus, and star.
- Tpn
TP"n"
- Transport Protocol, Class "n" (ISO 8073).
- TPS
- See transactions per second (TPS).
- trace
- A record of the execution of a computer program. A trace records the
sequence in which the instructions were executed.
- track
- A portion of a disk platter that can contain data.
- transaction
- In UNIX-based operating systems: An update to the filesystem
structure.
- transaction program
- In TCP/IP networking: An application program executed in response to
a transaction request. See also Transmission Control Protocol
(TCP).
- Transaction Services Layer
- In SNA networking: The functional layer that establishes a logical
interface for the end user.
- transactions per second (TPS)
- A rating of the performance of a computer system, based on the
average number of transactions the system can perform in one second.
- Transmission Control Layer
- In SNA networking: The functional layer that provides services
controlling the rate and sequence of data transmission.
- Transmission Control Protocol (TCP)
- Transmission Control Protocol (TCP) establishes a full-duplex and
reliable communication connection between two hosts. TCP receives outgoing
messages from higher layers and adds information to ensure that the message
arrives at the correct peer on the destination host. TCP also directs incoming
messages to the correct higher layer entity. TCP is most commonly used with the
Internet Protocol (IP) for a wide variety of data communications, including the
Internet. See also Internet,
Internet Protocol (IP).
- Transmission Control Protocol/Internet Protocol
(TCP/IP)
- A widely used networking protocol first developed for the Department
of Defense. It combines the Transmission Control Protocol (TCP) and the
Internet Protocol (IP). See also Transmission Control Protocol
(TCP), Internet Protocol (IP).
- transmission header (TH)
- In SNA networking: Control information in Layer 4 of the SNA
networking protocol that is created and used by path control to route message
units and to control their flow within the network.
- transmitter
- An electronic circuit that converts an electrical logical signal to a
signal suitable for the communications medium (optical or electrical). In the
Fiber Channel Bridge, a laser diode in the Gigabaud Link Module (GLM) component
assembly. See also bridge: In Fibre
Channel,Gigabaud Link Module (GLM).
- transparent data
- Data in a transmit data set that is not interpreted as containing
control characters. Transparent data is preceded by a control byte and a count
of the number of bytes of data that follow.
- Transport Layer
- In OSI network architecture: The layer responsible for providing
services to bridge the gap between the network layer and the session layer.
Transport functions deal with service quality and cost optimization (such as
error control, flow control, sequencing, and multiplexing). The transport layer
is often referred to as layer 4. See also Open
Systems Interconnection (OSI) reference model.
- Transport-Layer Interface (TLI)
- In TCP/IP networking: An alternative means by which an application
program gains access to the TCP/IP services. See also socket.
- Transport Library Interface
- A misinterpretation of TLI. Substitute "Transport-Layer Interface."
- transport service access point (TSAP)
- Under Construction..
- Trivial File-Transfer Protocol (TFTP)
- In TCP/IP networking: A standard TCP/IP protocol for transferring
files between systems.
- TSAP
- See transport service access point (TSAP).
- TSCL
- See Target System Control Library (TSCL).
- TSO
- See time-sharing option (TSO).
- TTY
- See teletypewriter (TTY).
- teletypewriter (TTY) line
- An RS-232-C transmission line used for connecting serial devices such
as terminals and printers.
- tunable parameters
- In UNIX-based operating systems: Values in the kernel that can be
changed to affect system performance. Also called configurable parameters.
- twisted-pair
- A transmission medium in which two insulated wires are twisted
together to reduce interference.
U
- UDP
- See User Datagram Protocol.
- UDP
- See User Datagram Protocol (UDP).
- UFS
- In the DYNIX/ptx-based operating system: A filesystem type derived
from the V4.2 Berkeley Fast filesystem.
- UID
- See User ID (UID).
- UKDI
- See United Kingdom domain identifier (UKDI).
- UKDP
- See United Kingdom domain part (UKDP).
- UKDSP
- See United Kingdom domain-specific part
(UKDSP).
- UKFI
- See United Kingdom format identifier (UKFI).
- unattended operation
- The automatic transmission and reception of messages without human
intervention.
- unbuffered I/O
- I/O that bypasses the filesystem cache for the purpose of increasing
I/O performance; also called "direct I/O."
- unformatted
- Describing a disk not yet ready to be used for storing data.
- uninterruptible power supply (UPS)
- A device connected between a computer and its power source that
protects the computer against blackouts, brownouts, and power surges. The UPS
contains a power sensor to monitor the supply and a battery to provide power
until an orderly shutdown of the system can be performed.
- uniprocessing
- Computation by a system with a single central processing unit (CPU).
- United Kingdom domain identifier (UKDI)
- In OSI networking: Under Construction.
- United Kingdom domain part (UKDP)
- In OSI networking: Under Construction.
- United Kingdom domain-specific part
(UKDSP)
- In OSI networking: Under Construction.
- United Kingdom format identifier (UKFI)
- In OSI networking: Under Construction.
- UNIX-to-UNIX copy (UUCP)
- In UNIX-based operating systems: a UNIX command that copies a source
file to a destination file.
- unmount
- In UNIX-based operating systems: To make (a filesystem) inaccessible
to users.
- unnamed fileset
- A fileset that contains files that are visible to and accessible by
users.
- upload
- To transfer data from a small (typically local) computer to a large
(typically remote) computer.
- upper multiplexer
- See multiplexer.
- upper stream
- A stream terminating above a multiplexer. The upstream end of an
upper stream originates at the stream head or another multiplexer driver.
- UPS
- See uninterruptible power supply (UPS).
- upstream
- The direction from the driver towards the stream head.
- USENET
- A major UNIX-to-UNIX copy (UUCP) network of computers across the
country having UUCP connections.
- use-once license
- In ptx/LICENSE: A type of license administered by the license server
that can be used for a single instance of invoking a product or of using a
service. The license server decrements the number of use-once licenses each
time the product is used.
- user account
- In UNIX-based operating systems: An entry in the /etc/passwd
file that defines a user's login name, ID, home directory, and default shell
program. The user's password, which is stored in the /etc/shadow file,
is also part of a user account.
- User Datagram Protocol (UDP)
- A connectionless and therefore unreliable means of transferring data
between machines.
- user file
- In ptx/LICENSE: A text file that specifies users who are allowed or
forbidden to use licensed software products.
- user ID (UID)
- In the UNIX operating system: A string that uniquely identifies each
user to the operating system.
- UUCP
- See UNIX-to-UNIX copy (UUCP).
- uugetty utility
- In UNIX-based operating systems: A program similar to getty
that allows a teletypewriter (TTY) line to be used for both logins and outgoing
calls. This program allows a modem to accept incoming calls and make outgoing
calls through the same port. See also teletypewriter (TTY)
line.
V
- variable
- A named entity to which a value is assigned, either on a command line
or in a file.
- variable-length record
- A record having a length independent of the length of other records
with which it is logically or physically associated. See also record, fixed-length
record .
- variable bit rate (VBR)
- A quality of service (QOS) class defined by the ATM Forum for
Asynchronous Tranfer Mode (ATM) networks. VBR is subdivided into a real time
(RT) class and non-real time (NRT ) class. VBR (RT) is used for connections in
which there is a fixed timing relationship between samples. VBR (NRT) is used
for connections in which there is no fixed timing relationship between samples,
but that still need a guaranteed QOS. See also Asynchronous Tranfer Mode (ATM),
quality of service (QOS).
- Vbad
- See VMEbus Adapter Board.
- VBIF
- See VMEbus Interface Board.
- VBR
- See variable bit rate (VBR).
- VC
- See virtual circuit (VC).
- VCC
- See virtual channel connection (VCC).
- VCI
- See virtual channel identifier (VCI).
- VCL
- See virtual channel link (VCL).
- VCS
- See Virtual Control Software
(VCS).
- VDT
- See video display terminal (VDT).
- vectored superuser privileges
- In DYNIX/ptx, the ability to assign certain superuser privileges to a
specific process ID, or to all processes invoked by a specific UID (user ID) or
GID (group ID).
- vendor password
- In ptx/LICENSE: A string encoded with information about a vendor
which, together with a vendor ID, establishes the vendor of a licensed product
in a license database.
- version identifier
- In ptx/LICENSE: A string by which the license server distinguishes
among different versions of a product.
- very large-scale integration (VLSI)
- Describing an integrated circuit incorporating 10,000 or more logic
gates.
- VEU
- See VMEbus Expansion Unit.
- VFS
- See Virtual File System (VFS).
- VGA Controller board
- A highly-scalable bus board required in WinServer systems to provide
an interface to the VGA monitor, keyboard, and mouse which make up the system's
VGA console.
- video display terminal (VDT)
- The combination of a video monitor, a keyboard, and typically some
graphically-oriented input device such as a mouse, acting together as the basic
input/output component of a computer system.
- virtual
- Describing a facility or path that appears to exist but does not
actually exist. For example, virtual memory is the use of disk-based storage to
simulate a larger address space than actually exists in system RAM.
- virtual channel connection (VCC)
- A logical circuit, made up of virtual channel links (VCLs), that
carries data between two end points in an Asynchronous Tranfer Mode (ATM)
network. Also called "virtual circuit connection." See also
Asynchronous Tranfer Mode (ATM), virtual channel link (VCL).
- virtual channel identifier (VCI)
- In OSI networking: A 16-bit field in the header on an Asynchronous
Tranfer Mode (ATM) cell. The VCI, together with the virtual path identifier
(VPI), is used to identify the next destination of a cell as it passes through
a series of ATM switches on its way to its destination. ATM switches use the
VPI/VCI fields to identify the next network virtual channel link (VCL) that a
cell needs to transit on its way to its final destination. See also
Asynchronous Tranfer Mode (ATM), virtual channel link (VCL), virtual path
identifier (VPI).
- virtual channel link (VCL)
- A connection between two Asynchronous Tranfer Mode (ATM) devices. A
virtual channel connection (VCC) is made up of one or more VCLs. See also
Asynchronous Tranfer Mode (ATM), virtual channel connection (VCC).
- virtual circuit (VC)
- A logical circuit created to ensure reliable communication between
two network devices. A virtual circuit is defined by a virtual path identifier
(VPI)/virtual channel identifier (VCI) pair, and can be either a permanent
virtual channel (PVC) or a switched virtual circuit (SVC). In Asynchronous
Tranfer Mode (ATM), virtual circuit is called "virtual channel." See also
Asynchronous Transfer Mode (ATM), switched virtual circuit (SVC), virtual
channel identifier (VCI), virtual path identifier (VPI).
- Virtual Control Software (VCS)
- A collection of system management services, accessible through a GUI
or remote interface, that allow a IBM NUMA system to be configured, booted,
controlled, and diagnosed.
- Virtual File System (VFS)
- A filesystem abstraction layer defined by an Open Systems
Interconnection (OSI) standard. VFS provides a uniform interface with any file
on a network, regardless of the filesystem in which it actually resides.
- virtual machine (VM)
- Software that performs like a hardware device; for example, a program
that allows applications written for an Intel processor to run on a Motorola
chip.
- virtual path identifier (VPI)
- An 8-bit field in the header of an Asynchronous Tranfer Mode (ATM)
cell. The VPI, together with the virtual channel identifier (VCI), is used to
identify the next destination of a cell as it passes through a series of ATM
switches on its way to its destination. ATM switches use the VPI/VCI fields to
identify the next virtual channel link (VCL) a cell needs to transit on its way
to its final destination. See also Asynchronous
Tranfer Mode (ATM), virtual channel identifier
(VCI), virtual channel link (VCL).
- Virtual Storage, Extended (VSE)
- A multiuser, multitasking operating system developed by IBM.
- Virtual Telecommunications Access Method
(VTAM)
- In SNA networking: A set of programs, designed by IBM, to control
communication between end-user devices and application programs running under
DOS/VS, VSE, OS/VS1, and OS/VS2.
- virtual terminal (VT)
- In networking: A process by which a network allows a variety of data
terminals with different protocols and formats to communicate with each other.
Each terminal's data is converted into a network standard format and then
converted into the format of the receiving device at the destination end.
- VLSI
- See very large-scale integration (VLSI).
- VM
- See virtual machine (VM).
- VMEbus
- An asynchronous parallel communications bus designed to support
high-speed communications among processor boards, memory boards, and peripheral
I/O controller boards. It is also known as ''IEC 821 BUS'' and ''IEEE
P1014/D1.2.''
- VMEbus Adapter Board (VBAD)
- A Highly Scalable Bus (HSB) board that provides the connection
between the Highly Scalable Bus and the VMEbus Interface (VBIF)
board in a VMEbus Expansion Unit (VEU). See also
Highly Scalable Bus (HSB), VMEbus,VMEbus Expansion Unit (VEU),
VMEbus Interface (VBIF) board.
- VMEbus Expansion Unit (VEU)
- The VMEbus card cage and interface boards used in S2000/4x0 and
S2000 7x0 systems. See also VMEbus.
- VMEbus Interface (VBIF) board
- A board that provides an interface between the VMEbus and the NUMA
system bus. See also VMEbus.
- VMS Record Management System (RMS)
- Under Construction..
- vnode
- Under Construction. See also snode.
- volume
-
- In data storage hardware: A removable physical unit of any
storage medium; for example, a tape reel or cartridge, a diskette, or a disk
pack.
- In ptx/SVM: The logical equivalent of a single hard disk The
logical components of a ptx/SVM volume, called plexes, are typically
distributed over several different physical disks for the sake of performance
or data protection. See also plex.
- volume table of contents (VTOC)
- In the DYNIX/ptx operating system: A partitioning driver. A VTOC file
contains disk geometry information and defines the sizes and starting points of
partitions on a disk.
- volume table of contents, nonstandard (VTOC, nonstandard)
- See nonstandard Volume Table
of Contents (VTOC).
- volume usage type
- Designates how ptx/SVM determines which plex in a volume contains the
most complete, up-to-date information after a system crash.
- VPI
- See virtual path identifier (VPI).
- VSE
- See Virtual Storage, Extended (VSE).
- VT
- See virtual terminal (VT).
- VT100
- A popular character-based video terminal developed by Digital
Equipment Corporation. Many later terminals offered the capability of operating
in VT100 emulation for network operations such as remote logins.
- VTAM
- See Virtual Telecommunications Access Method
(VTAM).
- VTOC
- See volume table of contents (VTOC).
- VTOC, nonstandard (volume table of contents, nonstandard)
- See nonstandard Volume Table
of Contents.
W
- WAN
- See Wide-Area Network (WAN).
- watermark
- A processing limit value used in flow control. Each queue has a high
watermark and a low watermark. The value of the high watermark indicates the
greatest number of bytes acceptable on the queue's message list. When the
number of bytes on the message list reaches the high watermark, the
flow-control mechanism blocks the preceding queue from sending messages to the
queue that has exceeded its high watermark. When the number of bytes is reduced
to the low watermark through service-procedure processing, flow control
unblocks the preceding queue.
- WCS
- See writable control store (WCS).
- well-known address
- An address available to a set of programs, applications, or other
processes. In ptx/TransACTION, for example, tmboot uses the
TUXCONFIG file to create a set of data structures in shared memory on
the master node, at an address known to all ptx/TransACTION processes.
- well-known port
-
In TCP/IP networking: A TCP/IP protocol port permanently assigned to
a service. All well-known ports for common services are agreed upon by the
Internet community. In ptx/TCP/IP, well-known ports are defined in the
/etc/services file. Also called a ''reserved port.'' See also
protocol port.
- wide-area network (WAN)
- A network in which widely separated computers are connected by
telephone lines or other means. Examples include X.25, Internet, MILNET, and
ARPANET. See also local-area network (LAN).
- Wide Quad-Channel I/O Controller
board
- A four-channel, wide-differential SCSI-2 controller board which
connects to the Symmetry System Bus (SSB) or Highly Scalable Bus (HSB). The
QCIC-W board controls up to 12 disk drives residing in Pbays on each channel,
for a total of 48 drives per board. A maximum of eight Quad-Channel I/O
Controller (QCIC) Board subsystems may be installed in an SE60 or SE70 system.
See also Highly Scalable Bus (HSB),
Pbay, Quad-Channel I/O Controller (QCIC) Board,
Small Computer Systems Interface (SCSI), Symmetry System Bus (SSB).
- wide SCSI
- An implementation of the Small Computer Systems Interface (SCSI)
standard. Wide SCSI allows up to sixteen devices, including the initiator or
bus controller, to be attached to the SCSI bus. See also Small
Computer Systems Interface (SCSI).
- wildcard
- See metacharacter.
- Win32
- An application programming interface (API) for the 386 processor's
32-bit mode, fully supported in Windows NT. Many functions are also supported
in Windows 3.1, and applications can be written to the Win32 subset (Win32s) to
gain improved performance on a 386 or higher processor running Windows 3.1 or
higher. Windows 3.1 translates the 32-bit calls in a Win32s application into
its native 16-bit calls.
- window manager
- In ptx/XWM: A client application that is used to manipulate windows.
The mwm window manager is provided with ptx/XWM.
- WinServer 5000 systems
- A collective term for the obsolete WS20, WS30, WS40, WS60, WS70, and
WS80 computer systems, all of which run the Windows NT operating system
supplied by Microsoft.
- workaround
- A suggested method by which a known problem can be avoided or
circumvented.
- workgroup cabinet
- A short IBM NUMA cabinet. See also NUMA-Q.
- working directory
- The current directory.
- workstation
- A powerful, single-user microcomputer, usually with a high-resolution
display. Workstations are often used in conjunction with networked applications
in which programs run on the workstation using data that resides on a server,
which is connected to the workstation by a network.
- wraparound
- See autowrap.
- writable control store (WCS)
- Under Construction.
- writeback
- In ptx/SVM: A volume-level feature that manages read errors.
- writecopy
- In ptx/SVM: A volume-level feature that goes into effect when
block-change logging is also enabled. Writecopy ensures the integrity of
mirrored plexes by preventing certain forms of data corruption, but can entail
a significant performance penalty.
- write permission
- In UNIX-based operating systems: On a directory, the capability to
modify contents (as with the cp and rm commands). On a file, the
capability to modify contents (as with the ed or vi editor). See
also read permission.
- write queue
- In a module or driver, the queue containing messages moving
downstream. The write queue is associated with a write(2) system
call and output from a user process.
- write-through cache
- A cache system in which all data writes are sent directly to system
memory, causing all caches with copies of that data to become invalid. Extra
time is required for the invalidated caches to be refilled with valid data.
Symmetry systems do not use write-through caching. See also
copyback cache.
X
- X
- See X Window System.
- X defaults
- See resource.
- XDR
- See External Data
Representation
- X/Open Portability Guide (XPG)
- A set of standards that specify compliance with X/Open's Common
Application Environment (CAE); for example, XPG3 (Release 3), introduced in
1989, specifies standards for UNIX System V Release 4.0.
- XPG
- See X/Open Portability Guide (XPG).
- X resources
- See resource.
- X Window System
- A network-based graphics windowing system developed by MIT. X
provides the foundation windowing system on which a graphical user interface
(GUI) can be built. OSF/Motif, for example, is a user interface built on
X.
- X.25
- The international protocol that defines how devices are connected to
a packet-switched network. These devices are typically larger computers,
mainframes, minicomputers, etc. Word processors, personal computers,
workstations, dumb terminals, and the like do not support the X.25 packet
switching protocols unless they are connected to the networkvia Packet
Assembler/Disassemblers (PADs). See also Packet
Assembler/Disassembler (PAD).