Using the SYSPROC and SYSEXEC files

TSO/E provides a system file, SYSEXEC, that can contain REXX execs only. You can use the SYSEXEC file to store execs in both TSO/E and non-TSO/E address spaces.

In TSO/E, the SYSPROC system file can contain REXX execs as well as TSO/E CLISTs. If you store a REXX exec in a PDS that is allocated to SYSPROC, the exec must begin with a comment and the first line of the comment must include the characters "REXX". This is required in order for the TSO/E EXEC command processor, during implicit execution, to distinguish REXX execs from CLISTs, which are also stored in data sets that are allocated to SYSPROC.

If you store your REXX execs in a PDS that is not allocated to SYSPROC, you do not need to begin the execs with a comment. However, it is recommended that you start all execs with a comment in the first column of the first line and include the characters REXX in the comment. In particular, this is recommended if you are writing REXX execs for use in other SAA environments. It is also recommended that you include the characters REXX in the first line of the comment to help users identify the program as a REXX exec.

If your installation will primarily use REXX, it is recommended that you use SYSEXEC for your REXX execs. Using SYSEXEC makes it easier to maintain your REXX execs and is also useful for execs that you use on other SAA environments. If your installation primarily uses CLISTs and does not plan to have a large number of REXX execs, you can use SYSPROC for your CLISTs and REXX execs.

With TSO/E, the author of a REXX exec can specify whether the exec should be compressed. A REXX exec is eligible to be compressed when the REXX exec is implicitly invoked and loaded from either SYSPROC or an application-level CLIST library defined by ALTLIB.

One use of compression is to reduce the size of an exec stored in VLF. Be aware that even if the exec cannot be stored in VLF (for example, VLF is not active) the exec can still be compressed. For details on REXX compression, refer to z/OS TSO/E Programming Guide and z/OS TSO/E REXX Reference.