Customizing REXX processing

TSO/E provides load modules, exits, and replaceable routines that you can use to customize REXX processing.

For REXX, TSO/E provides three default parameters modules that are load modules containing the default values for initializing language processor environments. A language processor environment is the environment in which a REXX exec executes. The parameter modules are:

IRXTSPRM for TSO/E
IRXISPRM for ISPF
IRXPARMS for MVS™.

You can change the default values used to initialize a language processor environment by providing your own parameters module. For more information, see Characteristics for a language processor environment.

The following describes the REXX exits:

Pre-environment initialization exit (IRXINITX)
IRXINITX performs processing before a new language processor environment is initialized. Use it to prevent the initialization of a language processor environment, change parameters used for initializing a language processor environment, or perform special pre-environment initialization processing.
Post-environment initialization exit (IRXITTS or IRXITMV)
IRXITTS performs processing after the new language processor environment is initialized for an environment integrated with TSO/E. Use it to perform special processing for a language processor environment initialized with the parameters of the IRXINITX exit.

IRXITMV performs processing after a new language processor environment is initialized for an environment not integrated with TSO/E. Use it to perform special processing for a language processor environment initialized with the parameters of the IRXINITX exit.
Environment termination exit (IRXTERMX)
IRXTERMX performs processing before a language processor environment is terminated. Use IRXTERMX to prevent the termination of a language processor environment or perform special processing with the parameters of the IRXINITX exit.
Exec processing exit
Use the exec processing exit to prevent the execution of a REXX exec or perform special processing before a REXX exec is executed.
Exec initialization exit
Use this exit to access and update REXX variables before the first clause in the exec is processed.
Exec termination exit
Use this exit to access and update REXX variables before the REXX variable pool is terminated.
Attention handling exit
Use the attention handling exit to perform special attention processing. This exit can only be used for an environment integrated with TSO/E.

For information about the REXX exits, see Customizing CLIST and REXX processing.

In addition to the REXX exits, TSO/E supplies replaceable routines you can use to customize REXX processing. TSO/E provides the following routines that handle different types of system services, which you can replace:

Loading and freeing execs
Reading and writing output
Handling data stack services
Obtaining and freeing storage
Obtaining the user or terminal ID
Determining whether the message ID is displayed with a REXX error message
Handling host commands for a specific language processor environment

For information about the replaceable routines, see Replaceable routines.