The application commits by issuing a checkpoint call.
At the time of the checkpoint, three actions take place:
IMS commits all the database updates and releases the
records for the checkpoint
IMS sends a message to the operator containing the ID of the
IMS writes a log record containing checkpoint information,
before and after images of the updated segments and the
Until the application issues the checkpoint, all segments which have been updated are ?enqueued? meaning any other programs attempting to access them will be forced to wait. If no checkpoints are taken, the commit will occur when the program completes.