| 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) Remote Site Recovery (RSR)
DBRC also plays a key role in managing the log data needed to restart and recover IMS online subsystems. 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, non-RSR batch environment), you can simplify your recovery process by using DBRC to supervise recovery and protect your databases.
Related Reading: IMS Version 9: Operations Guide provides detailed descriptions of recovery procedures with and without DBRC. You need to make two decisions about using DBRC. The first decision is whether or not DBRC is active in your IMS system. If you decide that DBRC is active, the second decision is whether databases must be registered to DBRC. Whether or not DBRC is active: DBRC is always active in an IMS control region (DBCTL, DCCTL, or DB/DC). You cannot override this. A BMP region does not have a DBRC execution parameter. DBRC is always active in the IMS control region that the BMP connects to. For batch and utility regions, you can use module DFSIDEF0 to specify whether or not DBRC is active. In DFSIDEF0, you can set DBRC= to YES, NO, or FORCE. The FORCE parameter forces DBRC usage in all other address spaces. FORCE cannot be overridden in the JCL. The YES, NO, and FORCE parameters control whether DBRC is active in an address space. The level of functions available is controlled by information in the RECON data set. Whether or not databases must be registered to DBRC: The option to force registration or not (NOFORCER or FORCER parameters on the INIT.RECON command) controls whether or not databases must be registered DBRC. Whether a database is registered to DBRC or not is recorded in the RECON data set. - If NOFORCER is specified, databases might, or might not be listed as being registered in the RECON data set. If a database is not in the RECON as being registered and DBRC is active, you get a warning message each time the database is opened. - If FORCER is specified and if DBRC is active in the address space, all databases must be listed in the RECON data set as registered. If the database is not registered, DBRC rejects authorization and the job abends (in DBCTL environments, the PSB fails to schedule, but the DBCTL region stays up).
If a database is listed in the RECON data set as registered and you run a job with DBRC=N, the next time you run a job with DBRC=Y, a warning message is issued flagging the fact the database has been accessed outside of DBRC control. You might want to take an image copy at that point. When you run a job with DBRC=N, there is an incomplete record of updates, which is useless for recovery purposes. |
