Data Guard Services

posted May 20, 2012, 6:23 AM by Sachchida Ojha
Log apply services automatically apply redo to standby databases to maintain synchronization with the primary database and allow transactionally consistent access to the data. By default, log apply services wait for the full archived redo log file to arrive on the standby database before applying it to the standby database.

Log Apply Services Configuration Options

  1. Using Real-Time Apply to Apply Redo Data Immediately : If the real-time apply feature is enabled, log apply services can apply redo data as it is received, without waiting for the current standby redo log file to be archived. This results in faster switchover and failover times because the standby redo log files have been applied already to the standby database by the time the failover or switchover begins.
  2. Specifying a Time Delay for the Application of Archived Redo Log Files: In some cases, you may want to create a time lag between the time when redo data is received from the primary site and when it is applied to the standby database. You can specify a time interval (in minutes) to protect against the application of corrupted or erroneous data to the standby database. When you set a DELAY interval, it does not delay the transport of the redo data to the standby database. Instead, the time lag you specify begins when the redo data is completely archived at the standby destination.

SQL Apply