Things to Consider When Allocating to a System File (SYSPROC
or SYSEXEC)
Allocating a partitioned data set containing execs to a system file allows you to:
v Run execs implicitly - After a PDS is allocated to a system file, you can run the
exec by simply entering the member name, which requires fewer keystrokes and
is therefore faster to invoke.
v Invoke user-written external functions and subroutines written in REXX that are in
PDSs also allocated to SYSEXEC or SYSPROC.
v Control search order - You can concatenate the data sets within the file to control
search order. This is useful in testing a version of an exec placed earlier in the
search order than the original version.
v Compression - In certain situations a REXX exec will be compressed to optimize
usage of system storage. These situations can arise only when the exec is
stored in either SYSPROC or the application-level CLIST file using the ALTLIB
command. The compression removes comment text between the comment
delimiters /* and */, removes leading and trailing blanks, and replaces blank
lines with null lines. Blanks and comments within literal strings or DBCS strings
are not removed. If the system finds the characters ″SOURCELINE″ outside of a
comment, the exec is not compressed. Additionally, if you do not want an exec to
be compressed, you can allocate the exec to the CLIST user-level file, or any of
the levels used for execs.
v Improve performance - Depending on your installation’s setup, you can affect the
performance of execs you run by allocating the data sets that contain them to
either SYSEXEC or SYSPROC. More about this technique appears in the
following sections on allocating to a specific system file.
Allocating to SYSEXEC
SYSEXEC is a system file that can contain execs only. SYSEXEC precedes
SYSPROC in the search order. Therefore execs in PDSs allocated to SYSEXEC
are retrieved more rapidly than execs in PDSs allocated to SYSPROC.
Allocating to SYSPROC
SYSPROC is a system file that originally contained only CLISTs written for
applications or for an individual’s use. SYSPROC now can also contain execs as
long as the execs are distinguishable from CLISTs.
The SYSEXEC file is searched first, followed by SYSPROC. If your installation uses
a large number of CLISTs that are in data sets allocated to SYSPROC and you do
not have a large number of REXX execs, you may want to use SYSPROC only and
not use SYSEXEC. To use SYSPROC only, a system programmer can change the
search order on an installation-wide basis, or an individual can change the search
order using the EXECUTIL SEARCHDD(NO) command. You can issue the
EXECUTIL SEARCHDD(NO) command directly from the terminal, from an exec or
CLIST, and from the JCL input stream run in TSO/E background. The ALTLIB
command can also affect search order. For general information about ALTLIB, see
“Appendix B. Specifying Alternate Libraries with the ALTLIB Command” on
page 195. For more information about the EXECUTIL and ALTLIB commands, see
z/OS TSO/E Command Reference.
Running Execs in a TSO/E Address Space
174
z/OS V1R1.0 TSO/E REXX User’s Guide
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