CA Datacom MUF upgraded from 14.0 to 15.0. CA Datacom 15.1 load library is using the same name that was previously used by the 14.0 one (e.g. SYS1.DATACOM.LOADLIB) and it is defined in LINKLIST. If 15.1 MUF region is started with this library in STEPLIB, it starts up fine but if this load library is removed from the STEPLIB, so it is used from LINKLIST, MUF loops, gets S0F4 abend or IEC909I 212-00
SYS1.DATACOM.LOADLIB was a PDS when running Datacom 14.0; now it’s a PDSE with 15.1. LLA must be correctly updated when the library format is changed from PDS to PDSE.
Use the load library from STEPLIB until LLA can be correctly updated. See IBM documentation about updating linklist with PDSE.