Multi-Instance Redo Apply

Reference documents ：

Oracle Data Guard and Oracle Real Application Clusters

D.1.1 Setting Up Multi-Instance Redo Apply

As of Oracle Database 12c Release 2 (12.2.0.1), a new INSTANCES [ ALL | integer] clause is available on the SQL ALTER DATABASE RECOVER MANAGED STANDBY DATABASE command.

It has the following restrictions:

• The clause is applicable only for Oracle Real Application Clusters (Oracle RAC) or Oracle RAC One Node databases.

• Block Change tracking is not supported.

• In-Memory column store is not supported with multi-instance redo apply in an Active Data Guard (ADG) environment.

The ALL option causes redo apply to run on all instances in an Oracle RAC standby database that are in an open or mounted state at the time recovery is started. .All instances must be in the same state — either open or mounted. A mix of states is not allowed.

The integer option restricts the number of instances that redo apply uses to the number you specify. For integer, specify an integer value from 1 to the number of instances in the standby database. The database chooses the instances on which to perform Redo Apply; you cannot specify particular instances.

The V$RECOVERY_PROGRESS view is only populated on the instance where recovery was started (where the MRP0 process resides).

If you omit the INSTANCES clause, then recovery happens on only one instance where the command was issued.

Because recovery processes ship redo among instances, redo apply performance is directly related to network bandwidth and latency.

-- Usually , Enable mrp process

alter database recover managed standby database disconnect from session;

-- from 12.2.0.1 Start ,mrp Processes can be started on all standby nodes

alter database recover managed standby database disconnect from session instances all;

[email protected]_stdby>select database_role from v$database;

DATABASE_ROLE
----------------
PHYSICAL STANDBY

[email protected]_stdby>alter database recover managed standby database disconnect from session instances all;

Database altered.

[email protected]_stdby>

-- You can also specify instance Up operation mrp process  

alter database recover managed standby database disconnect from session instances 1;

[email protected]_stdby>alter database recover managed standby database cancel;

Database altered.

[email protected]_stdby>alter database recover managed standby database disconnect from session instances 1;

Database altered.

[email protected]_stdby>

-- It can be downloaded from v$recovery_progress View some information . A little .

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