REX0023S

REX0023S  hh:mm:ss.ttt User field of environment block is zero. Invalid environment.
                       Information for subtask is not available.
Explanation:
Self explanatory. This is probably caused by a storage overlay.
Issued by:
TAURIP30
System administrator response:
Obtain an SVC dump of the address space using the z/OS DUMP command and send it to SupportLine along with the job log(s).