Recording information about opening and updating databases

After IMS opens a database, DBRC passes back the RECON data set initialization token (RIT) and any extended error queue elements (EEQEs) associated with each DBDS. The RIT allows IMS to determine whether the database has been used without DBRC or whether the database has been controlled by a different RECON data set.

Related reading:  See IMS Version 15 Database Administration for information on EEQEs.

When changes to DBDSs and areas occur, DBRC records information about these changes in the RECON data set. DBRC subsequently uses this information to determine which log data sets might contain change records for a given DBDS or area.

When a DBDS that is registered in the RECON data set is first opened for updates (or allocated), IMS tells DBRC to create an ALLOC record. In the case of a DEDB area, the ALLOC record is created when the area is first opened for update. The ALLOC record identifies the DBDS or area and contains the time stamp of the first update and the open time stamp of the corresponding PRILOG.

When DBRC creates the ALLOC record, DBRC also enters the name of the DBDS or area being changed in the LOGALL record for the PRILOG that is active at the time of the change.

When you deallocate (close) a DBDS or area using a /DBRECOVERY command from the operator console of the online IMS subsystem, DBRC writes a deallocation time stamp in the ALLOC record. If no de-allocation time is recorded, DBRC uses the closing time of the associated log as the deallocation time. Thus the RECON data set contains a list of the names of DBDSs or areas for which change records might exist on a given log data set (LOGALL record) and a list of the time ranges where changes could exist for a specific DBDS or area (ALLOC records) and a list of the logs containing the changes.