When are Error Handling Routines Needed?

Not all command processors require special error handling. In many cases, the error handling routine provided by the TMP is sufficient. However, if your command processor falls into one of the following categories, you should provide an ESTAE exit routine to handle abnormal terminations at the command processor 's task level:

command processors that process subcommands
command processors that request system resources that are not freed by abend or DETACH
command processors that process lists. Recovery processing is necessary to allow processing of other elements in the list if a failure occurs while processing one element.
command processors that use the STACK service routine to change the source of input. The error handling routine should issue the STACK macro to clear the input stack before returning to the TMP. Failure to clear the stack causes CLIST processing to be handled incorrectly.

In addition, if your command processor attaches subcommands, it should also provide an ESTAI exit to intercept abnormal terminations at the subcommand processor 's task level. ESTAE and ESTAI exit routines should be used in such a way that the command processor gets control if a subcommand abnormally terminates.

Figure 1 shows the relationship between the command processor, subcommand processor, and the error handling routines.

Figure 1. ABEND, ESTAI, ESTAE Relationship REQTEXT