IMSDB - DBRCwww.srinimf.com

DBRC

It is a part of IMS DB. We can recover and maintenance databases with it

The main functions are Log control Recovery control Share control

IMS to DBRC

RECONS

IMS communication with DBRC is performed through the use of three VSAM KSDS  data sets, called Recovery Control (RECON) data sets.

The RECON data sets  contain all of the recovery information used in recovering registered databases.   

RECON data sets contain several types of records, each of which is associated  with a particular function of DBRC

A RECON header record is created for each  RECON data set to provide information that DBRC uses in managing the system.  Other records are created to maintain log control, change accumulation, image  copy, database data set, reorganization, and recovery information.

Log Control

DBRC controls the use and availability of OLDS(online log datasets), SLDS, RLDS, and interim log  data sets.

Information about the logs is stored in a set of RECON data set  records called log data set records.

If you requested dual logging, they are  referred to as PRILOG (the primary log) and SECLOG, (the secondary log). DBRC  also creates log allocation (LOGALL) records to identify a database that was  changed while its log data set was open.

Recovery control

DBRC controls the recovery of databases by supplying the necessary input for  the IMS Recovery utility.

To use the recovery control portion of DBRC, you must  register your databases with DBRC.

Recovery control does not choose the correct  utility to be run at the correct time. For example, you must select the correct  utility to run in the following circumstances:▪ image copy after reorganization▪ recovery after database I/O error▪ backout after batch failure▪ /ERE after online failure

Full recovery

A full recovery means that you have restored all of the database updates that  were performed since the image copy was taken.

It requires a valid image copy of  the database, all log data sets created since the image copy was taken, and any  change accumulation data sets.

A full recovery is  most often used when the data has not been corrupted but the database has been  lost through something like a hardware or reorganization failure. The data was  not corrupted; the database simply crashed.

Timestamp recovery

A time stamp recovery recovers the database to a selected point in time.

A  time stamp recovery can use any image copy of the database. Then updates (using  logs and change accumulation data sets) are applied up to a selected point in  time.  

A time stamp recovery is usually used when the database has been corrupted  through a processing error such as faulty application logic.

Share Control

This can be achieved by registering database with dbrc, and to define share level

SHARELEVL 0 No sharing. The database can be accessed only by the subsystem to which it  has been authorized.

SHARELEVL 1 Database-level sharing. The owner subsystem can perform updates, but other  subsystems are read only.

SHARELEVL 2 Intra-host block-level sharing. Subsystems executing on the same MVS have  full update authority.

SHARELEVL 3Inter-host block-level sharing. Subsystems operating on the same (or any  other) MVS have full update authority.

References

Read more at:

ftp://service.boulder.ibm.com/eserver/zseries/audio/pdfs/Part_12_V9_DBRC.pdf

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