Terminating the DRA

Termination isolation means that a failure of the IMS DB subsystem does not cause a direct failure of any attached CCTL subsystem or ODBA application and vice versa.

Termination isolation should be one of your primary considerations when you design a CCTL subsystem or an ODBA application.

Although IMS DB was designed to prevent failure between connecting subsystems, a termination of a CCTL subsystem can cause IMS DB failure. If a DRA thread TCB terminates while IMS DB is processing a thread DL/I call on the CCTL's behalf, IMS DB fails with a U0113 abend.

The conditions that cause a thread TCB to terminate while IMS DB processes a DL/I call are:

• A DRA thread abend due to code failure. This can be corrected by fixing the failing code.
• The CCTL TCB collapses while a thread TCB still exists. The thread TCB collapses with an S13E or S33E abend and can result from three situations: a CCTL abend, a cancel command, or a shutdown.
• A DRA thread abend due to a IMS DB /STOP REGION CANCEL command initiated by CCTL.

An IMS DB U0113 abend can be prevented by designing the CCTL recovery process so that it issues a TERM request and waits for the request to complete. This allows the DRA and thread TCBs to terminate before the CCTL TCB terminates.