Sharing resources
Unless you indicate otherwise, the environments share the same
user files and message file. To avoid conflicting use of shared resources,
you should specify different ddnames using the MSGFILE runtime option,
and create distinctive user files for each environment.
Note: The
ENQ suboption of the MSGFILE runtime option can be used to provide
serialization around writes to the Message File. See z/OS Language Environment Programming Reference for
more information.