Recovering a dataguard standby after downtime
Recently, we had a planned weekend of standby downtime on a production system from Friday afternoon to Monday morning. This was all fine, and when the database came back up I expected it to just do it's FAL thing (Fetch Archive Log) and catch up automatically. Except I forgot 2 important things: Backups on this system are taken on the primary Archive log deletion policy on the primary is set to "BACKED UP 1 TIMES TO DISK" Thus when I came to start the redo apply on Monday morning, I found the archive logs had been deleted from the FRA on the primary and the standby couldn't recover automatically. That was when I started to feel that sinking feeling you get when you suddenly realise that you could have avoided this. I found out from the alert log which archive logs were needed. This shows in the alert log as something like this: FAL[client]: Failed to request gap sequence G AP - thread 1 sequence 27658-27658 DBID 123456789 branch 823623081