You can use the $JCTX macro extension service to add, expand, locate, and delete extensions to the job control table ($JCT) control block from this exit. For example, you can use these extensions to store job-related information. Extensions that are added can be SPOOLed extensions that are available to all exits that read the JCT or local extension that are available only to input processing exits (52, 53, 54, and 50) and the $QMOD exit (51). The size of SPOOLed extensions is based on the SPOOL buffer size and is less than 3K. You can have up to 8K of local extension regardless of SPOOL buffer size.