Upgrading CICS/CEMT from Batch mixing releases

Q:

I am upgrading to a new release of CMT.  Do the online and batch portions of the product have to be the same release?

A:

Generally yes, both batch and online CMT need to be the same release.
        
Release 5.0 used a different enquing mechanism than release 5.4. If you mix these two releases, you no longer single-thread batch jobs thru an applid. This allows batch jobs to overlay records on the BATCNTL file. The results are missing instructions, timeouts and return codes returning to the wrong batch jobs.