Default OMVS segment for MSCA?
The MSCA is not allowed to have an OMVS segment directly on it, but could use the default OMVS segment to assign it an OMVS segment.
After upgrading to zOS 2.1, the MSCA no longer can pick up the default OMVS segment because IBM removed support for a default OMVS segment.
Is there a way to add an OMVS segment to the MSCA?
The MSCA acid has always been considered a very limited use acid, best practices are to limit its use and generate SCA acids that will have similar scope to the MSCA to do your everyday administration.
For that reason it was never envisioned that the MSCA would need to be given the attributes of an OMVS user.
There are currently no plans to change this, and as a best practice is to use an SCA acid with an OMVS segment assigned to the acid.