DBCTL failures

A termination of a IMS DBCTL system does not cause connected subsystems to terminate; the subsystems are simply left without DBCTL services. If any of the DBCTL address spaces (DBC, DBRC, or DLISAS) fails, all of its address spaces are terminated.

The state of the DRA is determined by how the CCTL responds to notification of the IMS DBCTL system failure.

Normally, you terminate the IMS DBCTL system using a /CHECKPOINT FREEZE command, but you can also use the z/OS® MODIFY command to force termination, particularly if an IMS shutdown or failure results in a loop. If you use the MODIFY command and want a dump of the address space, use the DUMP keyword; otherwise use the STOP keyword. The DBCTL control region terminates with a U0020 abend, and IMS issues the following messages: DFS628I and DFS629I. These messages tell you that an abend is scheduled and what the job name is.

After determining the cause of the failure and correcting it, restart the IMS DBCTL system using the /ERESTART command. The CCTL cannot reconnect to the IMS DBCTL system until the /ERE command completes. The CCTL has several options on how to respond to a DBCTL failure.

When a CCTL connects to an IMS DBCTL system after a restart, they resynchronize in-doubt UORs automatically. Resynchronization means that the CCTL requests an action (commit, abort, or forget) and the IMS DBCTL system processes that request. If the commit or abort process fails, IMS takes the same actions as in the DB/DC environment. If the commit process fails for systems with DEDBs, IMS sends message DFS2282I to the DBCTL operator. For all failures, IMS removes the EEQEs because the UOR is no longer in-doubt.

If a CCTL that was connected to IMS fails, there could be in-doubt UORs. Normally, the CCTL can restart, reconnect to IMS, and resolve any in-doubt UORs. If the CCTL is cold started, the in-doubt UORs must be manually resolved with a /CHA CCTL command to commit or abort the UORs. This process will remove the EEQEs that are associated with the in-doubt UORs.

Do not attempt to in-doubt EEQEs directly by DBRC commands. Use the /CHA CCTL command to resolve the in-doubt UORs and clean up the EEQEs.

If a CCTL requests resynchronization of an indoubt UOR, and the DBCTL subsystem has no knowledge of that UOR, IMS returns code 218 to the CCTL, and sends message DFS2283I to the DBCTL operator. The DBCTL operator can use the /DISPLAY command to display the in-doubt UORs known to the IMS DBCTL subsystem.