I looked up dynamic allocation error code X'029C. I found this -
Meaning: There was a library automation communication services (LACS) mount failure for
a device in a IBM 3495 Tape Library Dataserver.
System Programmer or Operator Action: Depending
on the messages accompanying this error reason
code, different actions are needed. For
required actions, see the accompanying message.
This is not particularly helpful. There should be more messages which are not here, but it does appear to indicate why there was no mount message.