gtps4m0y | System Generation |
Unit record equipment may be used by low-priority batch-oriented entries (such as the generation of reports) which require printers or card readers as input/output devices. Utility programs such as card to tape, tape to printer, and so on, are provided and may be used in conjunction with user written routines. Unit record support itself is optional and is included/excluded based upon whether or not the user codes a UNITRD macro as part of his SIP input. Unit record support is by processor in a LC complex and by subsystem in a MDBF system.
Entries using unit record equipment tend to hold core blocks for a long period of time relative to the time required by other I/O devices. Thus, if indiscriminately activated, entries utilizing unit record equipment would impact the performance of the entire system. Priority tables in the unit record message editor program permit low priority unit record entries to be activated only when a predefined number of 136-byte storage blocks are available. Higher priority entries may be activated any time, thus the need for operator discretion.
Like general tapes, unit record devices are assigned to ECBs. This ensures consecutive printing and card reading. Unlike general tapes, however, no reserve unit record function is provided to pass control of unit record devices to another ECB for further processing.
The SIP UNITRD macro is used to specify the characteristics and requirements of unit record equipment. The Unit Record Status Table (see data macro UR1ST) contains information reflecting the status of the unit record devices. Six bytes per URST entry are contained in keypoint record B (CTKB). SIP uses the UNITRD macro parameters defining unit record devices to generate this information in macro CK9KC, the CTKB DSECT.
In an LC complex, only one Unit Record Status Table is defined. Since programs requiring unit record devices are invoked by operators, it is the responsibility of the central site operator to ensure that the unit record devices are switched to the desired processor within the complex before invoking a task requiring unit record devices.
The following parameters of the SIP UNITRD (unit record) macro relate to unit record support:
The Control Program Link Map Table is a control program CSECT which provides a directory of the control program CSECTs loaded to the online system. It is also used online by the same program for printing the control program link map table to the printer. The options are only available to users with unit record support.
Inclusion of unit record support is not required for use of the in-core dump formatter (ICDF) in a test system. Use of this facility is requested by the APRNT and DUMPDEV=TAPE parameters of the CONFIG macro. The same printer, as was specified by the APRNT parameter, may also be specified as a printer in the UNITRD macro.