In a system as complex as CICSPlex® SM, it makes sense to have a foundation of common components on which to build so that common functions can be provided by a single component. CICSPlex SM has many such building blocks that are used not only by all who require the service within a CMAS, but also within a MAS when the same services are required.
For a complete list of the major components of CICSPlex SM, see Major components of CICSPlex SM.
The role that Kernel Linkage plays in the transfer of control between methods was described in The structure of the CMAS. Kernel Linkage also has several subcomponents that provide services related to maintenance of the basic CICSPlex SM environment:
Controls the synchronization between components and provides a common means for identifying the status of components.
Provides a flexible way for components to notify interested parties of events, such as the starting of a MAS. It also provides the means for components to register their interest in specific events.
Supports the distribution of requests to multiple CMASs and MASs and the consolidation of results.
Kernel Linkage also controls the interface between code running under the MVS™ TCBs (selectors) and code running under the CICS® TCB (methods).
This component has an identifier of KNL and its module names have the characters XL in the fifth and sixth positions (for example, EYU0XLNE).
Trace Services provides other CICSPlex SM components with the ability to write trace records to the CICS trace table and trace data sets. Trace Services is also responsible for writing any trace records created by a MAS to the trace table and data set of the managing CMAS. Tracing is a key part of CICSPlex SM serviceability. Because a failure could occur at any time during CICSPlex SM processing, Trace Services initializes as early as possible and terminates as late as possible in CICSPlex SM processing.
This component has an identifier of TRC and its module names have the characters XZ in the fifth and sixth positions (for example, EYU0XZPT).
The Message Services component provides a common facility for building and issuing MVS console messages. The fixed text of messages and the variable text fragments used for insertion are defined in prototype tables. Calling methods then ask for messages by number and insert the appropriate variable text. Message Services is also responsible for creating the consolidated message log called EYULOG and for writing MAS-generated messages to the managing CMAS.
This component has an identifier of MSG and its module names have the characters XM in the fifth and sixth positions (for example, EYU0XMSM).
The Common Services component provides basic system services such as GETMAIN, FREEMAIN, POST, and WAIT processing. By routing all requests for these services through a single component, most CICSPlex SM modules are isolated from the real environment in which they run. As a result, a relatively few methods (those that make up Common Services) need to be aware of the details of how these services are requested. One of the Common Services subcomponents provides timing services using the control task that runs as an MVS TCB. Another subcomponent provides locking services, both local (within a CMAS or MAS) and global (between a CMAS and its local MASs).
This component has an identifier of SRV and its module names have the characters XS in the fifth and sixth positions (for example, EYU0XSCG).
The Data Cache Manager component implements logical cache storage for use by CICSPlex SM components. Each component can request a cache allocation and can allocate cache blocks within it. Several additional services are also provided by the Data Cache Manager:
This component has an identifier of CHE and its module names have the characters XC in the fifth and sixth positions (for example, EYU0XCLA).
The Queue Manager component implements queues of data within a cache that is shared between a CMAS and all its local MASs. Queues are often used to communicate between different CICSPlex SM methods when the data to be passed is a set. Records within a queue can be accessed either sequentially or directly by relative record number.
This component has an identifier of QUE and its module names have the characters XQ in the fifth and sixth positions (for example, EYU0XQGQ).
The Data Repository component provides methods for creating, accessing, updating, and deleting data in the CICSPlex SM data repository, which is the VSAM data set where system configuration and definition data is stored. This component provides referential integrity support for the data repository and ensures proper rollback if an operation is only partially successful. Within this component are the following subcomponents:
This component has an identifier of DAT and its module names have the characters XD in the fifth and sixth positions (for example, EYU0XDGR).
Communications is one of the most complex components of CICSPlex SM. It is made up of many subcomponents that provide all the services for implementing CMAS-to-CMAS and CMAS-to-MAS communication. In addition to the Communications component, CICSPlex SM makes use of MVS program call routines in the ESSS. For communication between a CMAS and its local MASs, these program call routines provide cross-memory services for more efficient communication.
Communication between one CMAS and another CMAS, can
use either CICS intersystem communication (ISC) or interregion communication (IRC) services (usually referred to as
multiregion operation, or MRO). Because routing of messages around
the CMAS network does not require the user to define path or routing
information, a subcomponent of Communications maintains a dynamic topology of the
network and determines routes as required.
The Communications component implements a simple model for all other CICSPlex SM components, that of remote method call. A method merely builds a MAL and invokes Communications via the Access Services subcomponent, specifying the destination and type of processing required. Communications then transports the MAL and causes it to be run in the target locations. All data required for the remote running of a method is automatically transported as well. Because all methods and their MALs are clearly defined, Communications knows what data must be sent to the target and what data must be returned to the caller. The data that is transported can be simple data in a MAL itself, data pointed to by a MAL, or CICSPlex SM queues or cache lists.
This component has an identifier of COM and its module names have the character C in the fifth position (for example, EYU0CSLT).
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