There are many exit routines you can use to customize REXX processing. The exits differ from other exit routines that TSO/E provides, such as exits for TSO/E command processors. Some of the REXX exits have fixed names while others you name yourself. Several exits receive parameters on entry and others receive no parameters.

Generally, you use exit routines to customize a particular command or function on a system-wide basis. You use the REXX exits to customize different aspects of REXX processing on a language processor environment basis. The following highlights the exits you can use for REXX. z/OS TSO/E Customization describes the exits in more detail. However, many of the exits receive the parameters that a caller passed on a call to a REXX routine, such as IRXINIT and IRXEXEC. Therefore, you will need to use z/OS TSO/E Customization and this book for complete information.

Some of the REXX exits do not have fixed names. You supply the name yourself and then define the name in the appropriate fields in the module name table. In the module name table, you also define the names of replaceable routines you provide. However, unlike the replaceable routines, which you can provide only in language processor environments that are not integrated into TSO/E, you can use the REXX exits in any type of environment (integrated and not integrated into TSO/E). One exception is the attention handling exit, which is available only in TSO/E (in an environment that is integrated into TSO/E).