Overview of DBRC

A feature of the IMS Database Manager that facilitates easier recovery of IMS databases, DBRC maintains information that is required for database recoveries, generates recovery control statements, verifies recovery input, maintains a separate change log for database data sets, and supports sharing of IMS databases and areas by multiple IMS subsystems.

DBRC is an integral part of IMS. IMS relies on DBRC to record and manage information about many items. DBRC keeps this information in a set of VSAM data sets that are collectively called the recovery control (RECON) data set and advises IMS (based on the information in the RECON data set) about how to proceed.

Specifically, DBRC:

Helps you ensure IMS system and database integrity by recording and managing information associated with the logging process.
Assists IMS in the restart process by notifying IMS which logs to use for restart.
Assists IMS to allow or prevent access to databases in data-sharing environments by recording and managing database authorization information.
Facilitates database and log recovery by:
- Controlling the use and integrity of the information in the logs.
- Recording and maintaining information about the databases and logs in the RECON data set.
- Generating and verifying the Job Control Language (JCL) for various IMS utility programs.
Supports Extended Recovery Facility (XRF) by identifying (in the RECON data set) if the subsystem is XRF capable.
Supports IMSplexes by:
- Notifying all DBRCs in the same IMSplex within the same DBRC sharing group when one of the DBRCs performs a RECON data set reconfiguration.
- Allowing parallel access to the RECON data set.

DBRC also plays a key role in managing the log data needed to restart and recover IMS online subsystems.

Most IMS configurations require DBRC, including:

Online configurations: DB/DC, DCCTL, or DBCTL
Data-sharing environments, including IMSplexes
Configurations that use Extended Recovery Facility (XRF)

Attention: DBRC is not required for IMS batch jobs and for some offline utilities. However, if batch jobs and utilities that access registered databases are allowed to run without DBRC, the recoverability and integrity of the databases could be lost. Even if your configuration does not require the use of DBRC (such as in a non-data sharing, batch environment), you can simplify your recovery process by using DBRC to supervise recovery and protect your databases.

Related reading:

IMS Version 15 Operations and Automation provides detailed descriptions of recovery procedures with and without DBRC.
How DBRC helps in recovery further describes how DBRC helps with database recovery.