What version OS are you running and are you up to the latest PTF’s? Do you get any other messages in your joblog? Is there anything special about the files that you receive the message on? Are all/some of these files journalled?
This may well be caused by using *SYNCLIB with *ALLUSR – this means that the system has to keep track of ALL the objects in *ALLUSR libraries to ensure there is a “checkpoint” where none of the objects are being updated. I would suggest you use *LIB instead of *SYNCLIB – or does that cause the same problem?