In a test MICS instance I had a few issues trying to create HISTW and HISTM tapes. Part of the issue was with our SMS trying to push the datasets to disk, but even when I got that changed I sill ran into issue. I went to the PIOM and found that new technique was available to use actual volser in place of NULSER. It wasn't clear all changes I needed to make and what GEN's I needed to run. Once I get this worked out in the test MICS instances, I'd like to put the same in play in our prod MICS instances. I need a list of what I need to do in both test and prod to make use of this.
Make the change(s) in your 'p.PARMS(JCLDEF) member. In that member there is NULLSER and NULLUNIT parms. For NULLSER, you would specify the actual volser, and for NULLUNIT, you would specify the generic unit identifier. After, run a 'p.CNTL(JCLGENB)' that will basically re-gen everything at your unit level.