You can check on the official doc.. Oracle® Data Guard Concepts and Administration http://download.oracle.com/docs/cd/E11882_01/server.112/e10700/toc.htm 7.3.3 Monitoring Redo Apply on Physical Standby Databases And these comprehensive Metalink notes.. 11gR1 Dataguard Content Doc ID: 798974.1 10gR2 Dataguard Content Doc ID: 739396.1 - Karl Arao http://karlarao.wordpress.com -- //www.freelists.org/webpage/oracle-l