User exits

User exits identify points in binder processing when the calling program regains control. The binder passes the user exit routine a data buffer. The exit routine can examine or modify the data, return it to the binder, and set a return code.

The binder provides user exit points for:

All messages (or those above a specified severity) issued during processing
Each successful or failed attempt to save a program object or load module
Each linkage of an external reference to its target

You can define the user exits either using the EXITS parameter on a FUNC=STARTD call or by specifying them in the EXITS invocation option. Note that invocation options are passed one of four ways:

Through the JCL PARM string for batch invocation
Via PARAM when using ATTACH, LINK, or SCTL
Pointed to by register 1 when using LOAD and CALL
Within the OPTIONS string of FUNC=STARTD when using the API

If the EXITS option is found in the OPTIONS string passed by FUNC=STARTD when the API is used, that will override any EXITS parameter also passed by FUNC=STARTD.

Note: In this topic, you will see several references to "varying string." Keep in mind that a varying string consists of a halfword length field followed by a character string of that length and that varying strings are always addressed by pointing to the length field.