I've just activated Restart Manager by modifying the PGM MIMDRBGN with MIMDRRM in my CAMIMGR proc. I found the following lines in the SYSLOG:
MIMRM07I No Steplib found
MIMRM11F Load library for MIM must be a PDS
IEF450I CAMIMGR CAMIMGR - ABEND=S000 U0040 REASON=000000A8 209 TIME=17.55.04
The MIM loadlib MUST be defined in the STEPLIB concatenation and MUST NOT be a PDSE.
Verify that the MIM loadlib is not a PDSE and define a STEPLIB DD to the MIM startup referencing the MIM loadlib.