gtps4m2x | System Generation |
The IODEV macro is used to specify the characteristics and system requirements for specific input/output (I/O) devices. Each disk, 37x5 communication control unit, 3088 addresses used by SNA CTC (DVTYP=SCTC), or tape I/O device which is uniquely addressable must be specified with an IODEV macro.
In a multiple database function (MDBF) environment, all subsystems use the highest and lowest channel addresses calculated from the basic subsystem.
For 37x5 communication control units and SNA channel-to-channel (CTC) connections, only one symbolic device address can be coded per use of the IODEV macro. The total number of 37x5 communication control units and SNA CTC connections defined by the IODEV macro cannot exceed 255. This information is used to build the Symbolic Device Address Table (SDAT).
A symbolic device address associated with a 37x5 communication control unit running EP only or with the EP portion of a communication control unit running PEP must not be specified using the IODEV macro. Instead, the NETWK macro is used to specify 37x5 communication control units running EP.
For tape devices, an entry is created in the Tape Control Unit Cross Reference Table (COSY) for each IODEV coded. This table is used for validation during restart and tape reconfiguration. Each logical channel/control unit value specified defines a tape subsystem; up to 16 devices may be configured on a subsystem. It is recommended that sufficient tape subsystems are generated to allow for expansion without the need for regeneration. Tape drives are added online, and the results are keypointed (CTK0, CTK1, and CTKB), and thus preserved across a system IPL.
Format
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For DASD devices, this address will encompass eight units/spindles. The symbolic device address must consist of four hexadecimal digits, must be in the range X'0100' to X'7FF8', and the last digit must be either a zero or an eight. The first two digits represent the logical channel number where the device is attached. The third and fourth digits represent the logical control unit, the string address, and the starting device number. For more information and examples refer to Database Device Addressing.
For tape devices, IOADR must consist of two hexadecimal digits (X'10' to X'FF') that represent the logical channel/control unit subsystem.
Note that the device numbers specified in the source for the IOCP represent symbolic (logical channel/control-unit/device) addresses to TPF.
A channel address of 0 should not be used for DASD or tape devices.
For 37x5 communication control units or SNA CTC connections this address defines one specific symbolic device address (SDA). The symbolic device address must be a four-digit hexadecimal value in the range X'0001' through X'7FFF'.
Code this parameter only when DVTYP=DASD and when this DASD string is serviced by a 3990 Record Cache Subsystem Control Unit. If DVTYP is not equal to 'DASD', RCSSID is ignored.
RCSSID accepts any four-digit hexadecimal number in the range X'0001' to X'FFFF', inclusive. If you fail to code RCSSID for 3990 cached DASD strings, an improper record cache subsystem status table may be created at load time.
Examples
Example 1: The following specifies a DASD string with eight devices connected on address 01A0.
IODEV DVTYP=DASD,IOADR=01A0 /* UNITS 01A0-01A7 */
Example 2: The following specifies a DASD string with 16 devices connected on address 01A0.
IODEV DVTYP=DASD,IOADR=01A0 /* UNITS 01A0-01A7 */ IODEV DVTYP=DASD,IOADR=01A8 /* UNITS 01A8-01AF */
Example 3: The following specifies a TAPE subsystem that defines logical addresses 180-18F.
IODEV DVTYP=TAPE,IOADR=18
Example 4: The following specifies a 37x5 communication control unit with an address of X'1C' and an SNA CTC connection on symbolic address X'752E'.
IODEV DVTYP=37X5,IOADR=001C IODEV DVTYP=SCTC,IOADR=752E
References