Recovery in an IMS DBCTL environment

The IMS DBCTL environment consists of the IMS Database Manager (not the Transaction Manager) and allows one or more transaction management subsystems, such as CICS®, to access DL/I databases and DEDBs.

These transaction management subsystems are known as coordinator controllers (CCTLs). A CCTL communicates with the DBCTL subsystem using an interface called the database resource adapter (DRA). Connections or paths between a DBCTL control region and a CCTL are created as part of CCTL initialization. These connections are called threads.

Because the CCTL is a separate subsystem, failures are isolated between the IMS DBCTL subsystem and the CCTL. That is, failure of the DBCTL subsystem does not generally cause the CCTL to terminate. Likewise, failure of a CCTL does not generally cause failure of the DBCTL subsystem. Generally, the only time a CCTL failure can affect the DBCTL subsystem is if the CCTL had one or more threads executing in DL/I at the time of its failure).

An IMS DBCTL subsystem cannot restart from log data not created by a DBCTL subsystem. Likewise, non-DBCTL IMS subsystems cannot restart using log data created by a DBCTL subsystem. In other words, restarts of an IMS DBCTL subsystem must use log data produced by that system. You can, however, perform database recovery using a combination of log data sets created by other subsystems: IMS DB/DC, batch, or DBCTL.

Because DBCTL requires the DBRC log control facility, you must use DBRC with DBCTL. Log records produced by an IMS DBCTL system are compatible with an IMS DB/DC system (except for subsystem restart).