Exit 8: RESERVE exit

This user exit lets you use your own method for serializing resources in addition to the RESERVE done by ISPF. See ISPF enqueue processing for data integrity for information about ISPF's use of ENQ and RESERVE. ISPF gives control to the exit routine before it does the RESERVE. If your serialization mechanism cannot acquire the resource, or if the exit routine returns a code greater than 0, ISPF does not attempt to get it.

The RESERVE exit is still called if Configuration table keyword PDSE_RESERVE_PROCESSING is set to OFF.

Exit parameters

In addition to the standard exit parameters described in Exit parameter list, the exit routines at this user exit receive these parameters. ISPF ignores any changes made to these parameters.

qname

An 8-character field that contains the queue name against which the RESERVE is done. (ISPF uses a qname of 'SPFEDIT '.)

rname

The 44-character resource name (data set name) that is reserved.

ucbaddr

A fullword field containing the address of the unit control block (UCB) for the reserved device.

Flags

4 bytes of bit flags defined as follows:

0: 1 = Exclusive reserve requested. 0 = Shared reserve requested. (ISPF always requests exclusive use of the resource at RESERVE.)
1: 1 = A RESERVE or ENQ will be done on qname 'SYSIEWLP' (the linkage editor qname).
2: 1 = The resource being reserved is a partitioned data set.
3: 1 = The resource being reserved is a sequential data set.
4: 1 = The resource being reserved is a PDSE.
5: 1 = PDSE_RESERVE_PROCESSING setting. On by default
6-31: Reserved.

Note: The exit routine should not use the same (qname, rname) combination (in a RESERVE macro call) that ISPF uses. If that happens, an abend occurs when ISPF attempts to do its own RESERVE.

Return codes

0: Normal completion; ISPF does its own RESERVE and continues processing.
16: Resource not available. ISPF issues a message showing that the exit routine indicated the resource is not available. This results in a failure of the service requesting the RESERVE.
Other: ISPF treats other return codes similar to a return code of 16 and issues a message indicating that the exit routine returned an incorrect return code.