After upgrading or applying maintenance to the z/OS environment, users seem to have encounter S0C4 abends at offset x'3B' in XCOMJOB. In addition to the abend they have also experienced XCOMJOB hanging.
To resolve the problem please verify that you have Common Services 14.1 installed and apply Common Service fix RO78180 and any of its pre-requisites. The fix allows XCOM to use Symbol Substitution Service correctly.