In a previous post, we have seen various methods to create Physical Standby Database.

Create Standby Database using duplicate database for standby RMAN command

In this post, we will see how archive logs are transferred and recovered from a standby database and concern processes for redo transport and recovery.

There are main two processes in Data Guard Physical Standby.

  1. RFS
  2. MRP

1. RFS Process: Process is responsible to archive log transfer. When the log switch occurs at the Primary database, LNS process of primary database captures redo and sent it to Standby using Oracle Net.

Let us see the example.

Step 1: Switch logfile at Primary Database :

Check alert log of standby database :

Here we can see whenever log switch occurs at Primary, RFS process adds an entry of archive log to standby database.

Let’s check it in v$managed_standby view.

2. MRP Process: MRP process applies archived redo log information to the physical standby database that is captured by RFS process at standby.

How to start MRP?

We can start MRP [recovery] using RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION.

As we have used disconnect from the session, recovery will be started in background session. If we don’t use it it will be started as a foreground session.

Once we start recovery MRP process will awake and recover all archive logs pending from last applied archive log.

We can check recovery process in alert log also.

check recovery process with SQL query.

Now, Stopping recovery process.

We can stop recovery process using recover managed standby database cancel command.

Stay tuned for More articles on Oracle DataGuard

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