1. Oracle GoldenGate Classic Architecture Documentation
  2. Administer
  3. Performing Administrative Operations
  4. Restarting a Primary Extract after System Failure or Corruption
  5. Details of This Procedure

Details of This Procedure

Extract passes a log begin sequence number, or LOGBSN, to the trail files. The BSN is the native database sequence number that identifies the oldest uncommitted transaction that is held in Extract memory. For example, the BSN in an Oracle installation would be the Oracle system change number (SCN). Each trail file contains the lowest LOGBSN value for all of the transactions in that trail file. Once you know the LOGBSN value, you can reposition Extract at the correct read position to ensure that the appropriate transactions are re-generated to the trail and propagated to Replicat.

Note:

In an Oracle RAC environment, the lowest SCN of all of the threads is transmitted to Replicat. Transactions that may already have been committed by Replicat are handled as duplicates at startup. However, any thread that has been idle past a certain threshold will not be considered for the BSN value, to avoid Extract having to read too far back in the log stream when restarted.

The bounded recovery checkpoint is not taken into account when calculating the LOGBSN. The failure that affected the Extract checkpoint file may also involve a loss of the persisted bounded recovery data files and bounded recovery checkpoint information.