CAUTION: IBM® does not recommend or support modifications to JES2 source code. If you assume the risk of modifying JES2, then also assure your modifications do not impact JES2 serviceability using IPCS. Otherwise, IBM service LEVEL2 support might not be able to read JES2 dumps taken for problems unrelated to the modifications.

Avoid expanding JES2 control blocks. Use alternatives such as:

1. Use fields dedicated for installation use that appear in many major control blocks. Place your data, or a pointer to your data, in these fields. However, beware of setting storage address in checkpointed or SPOOL resident control blocks.
2. Use $JCTX services rather than modifying $JCT.
3. Use table pairs and dynamic tables. For example, use dynamic $BERTTABs with CBOFF=* instead of modifying $JQE.

This is a partial list. Evaluate your specific situation and take the appropriate action.