Compress request exit

In the ISPF configuration table keyword file, this exit is set with the keywords COMPRESS_UTILITY_PROGRAM_EXIT (if your exit is a program) and COMPRESS_UTILITY_CLIST_EXIT (if your exit is a CLIST).

Instead of using the IEBCOPY system utility interface that PDF provides, you can specify that PDF use an installation-written exit routine to handle requests to compress partitioned data sets under options 3.1, 3.4, and the LMCOMP service. When the compress exit gets control, the data set will have already been allocated and enqueued as exclusive. The exit will have to re-allocate the data set to a specific ddname. As part of termination processing, the exit must free the allocated ddname. The FREE operation must not be done by data set name. PDF allows the exit routine to:

Use an alternate compression technique
Provide backup before allowing normal PDF compression
Selectively prevent compression.

PDF calls the exit routine with the SELECT service. The routine can be either a program or CLIST. All ISPF and system services are available.

Exit parameters

PDF communicates with the exit routine through variables in the shared pool. PDF considers these variables to be read-only and ignores any changes the exit routines make to the parameters. A VERASE is done at the end of the compress to delete the variables from all variable pools.

The variables available to the compress exit routine are:

Table 1. Details of the variables available to the compress exit routine
Variable	Type	Len	Description
ZCMPDSN	CHAR	44	Fully qualified data set name with no quotes
ZCMPVOL	CHAR	6	Volume serial
ZCMPPSWD	CHAR	8	Data set password
ZCMPORIG	CHAR	8	Origin of the call. LMCOMP The compress service (LMCOMP) called the exit routine. OPTION31 The compress exit routine is being called from option 3.1, the compress utility. OPTION34 The compress exit routine is being called from option 3.4, the data set list utility.

Return codes

0: Data set successfully compressed
2: PDF should compress the data set
4: Data set is not eligible for compression
8: Data set could not be allocated
12: Data set not cataloged
16: Error in exit; PDF should continue processing
17: LMCOMP recursion error
18: Unknown return code from exit
19: Error encountered invoking exit
20: Severe error; PDF should not continue processing
Other: PDF treats the error as return code 16.

Error processing

The exit routine is responsible for handling all errors that occur while it is in control. Failure to use correct allocation, serialization, and deallocation causes unpredictable results.