We are sometimes asked why we discourage use of ZMF-related sessions (e.g. the ISPF UI, XMLSERV, etc.) in split screen mode? For example, why do users sometimes see the following messages?

IKJ56246I FILE SERNQ NOT ALLOCATED, FILE IN USE
****************************************************
* *
* Using multiple concurrent ZMF/Sernet sessions *
* in split screen mode is not recommended. *
* *
* Doing so is not supported by Micro Focus. *
* Continue at your own risk! *
* *
****************************************************
Continue? (Y/N)

Some background explanation can be found in longstanding KB article S101042.