12.2新特性之ADG多節點啟動MRP程式

parknkjun發表於2019-03-05

12.2新特性，ADG是RAC環境，在多個例項可以啟動MRP程式recover，命令如ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION INSTANCES ALL

該特性只適用RAC和RAC one node環境資料庫,不支援塊跟蹤,不支援In-Memeory列儲存
注：MRP程式只在執行命令的節點執行，其他節點會產生pr* recovery processes程式。

D.1.1  Setting Up Multi-Instance Redo Apply

As of Oracle Database 12 c  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.


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