The exit receives the JCL statements built by the logon processor. The logon processor constructs JOB and EXEC statements. If the logon pre-prompt exit IKJEFLD or IKJEFLD1 changed the JCL parameter, this exit receives those JCL statements in place of the JCL statements the logon processor constructs. The JCL defines terminal job resources. The exit can modify the statements it receives, or it can add additional statements.

The JCL parameter is 800 bytes in length, in which the exit can return a maximum of ten JCL statements. To return more than ten JCL statements, the exit can provide its own JCL parameter. Your installation's JES capability determines the actual number of JCL statements you can return. Logon processing does not check that number. To provide your own JCL parameter, replace the parameter address supplied by the LOGON command with the address of the alternative parameter. Then set the current length to the number of JCL statements multiplied by 80.

The logon processor expects that each 80 bytes of the parameter contains a full 80-byte JCL statement in standard format. If your JCL statements are shorter than 80 bytes, pad them with blanks. The logon processor uses the current length field of the parameter to determine the number of statements that the exit is returning (current length/80 = n statements).

If you issue the GETMAIN macro to obtain storage for an alternative JCL parameter, you must use a job-oriented subpool (such as subpools 0–127). Storage is freed automatically when the logon job ends. Otherwise, you can use the user word to save the address so the logoff exit IKJEFLD2 can access it and issue the FREEMAIN macro to free storage in the subpool.