• Arun Kumar

Data Guard Background Processes

When you query v$managed_standby on physical standby database, you will observe thee main background processes:

  • Archive Process

  • RFS Process

  • MRP Process

Data Guard Archive Processes

We have seen 4 numbers ARCH processes when you query v$managed_standby.

That’s alright, because of 4 is the default value of LOG_ARCHIVE_MAX_PROCESSES.

The LOG_ARCHIVE_MAX_PROCESSES initialization parameter specifies the number of ARCn processes that the database initially starts. The default is four processes. There is usually no need specify this initialization parameter or to change its default value, because the database starts additional archiver processes (ARCn) as needed to ensure that the automatic processing of filled redo log files does not fall behind.

However, to avoid any run-time overhead of starting additional ARCn processes, you can set the LOG_ARCHIVE_MAX_PROCESSES initialization parameter to specify that up to 30 ARCn processes be started at instance startup. The LOG_ARCHIVE_MAX_PROCESSES parameter is dynamic, so you can change it using the ALTER SYSTEM statement.

Source: Oracle Database Administrator’s Guide

In most cases the default for LOG_ARCHIVE_MAX_PROCESSES is sufficient. However, in a Data Guard configurations that have multiple standby databases it may be necessary to increase the number of archive processes. The value of the LOG_ARCHIVE_MAX_PROCESSES initialization parameter must be at least one greater than the total number of all remote destinations. Use the following equation when setting the LOG_ARCHIVE_MAX_PROCESSES parameter for highly available environments:

LOG_ARCHIVE_MAX_PROCESSES = sum(remote_destinations) + count(threads)

Source: Set the LOG_ARCHIVE_MAX_PROCESSES Parameter

Data Guard RFS Processes

3 Numbers of RFSprocesses

RFS processes are spawned regarding the amount of remote archiver connections (due to ARC in your DG configuration). One ARC process is related to local archiving on primary database and so 3 are left for DG transmission  … this can be parallelized as well, but needs additional parameter setting MAX_CONNECTIONS.

Data Guard MRP Process

1 number of MRP0process

How many “Managed Standby Recovery Processes” do you expect? It is the coordinator – and like in real life only one guy is the boss

The ARCH redo transport mode has been deprecated and will be desupported in a future release. Oracle recommends that you switch to the ASYNC transport mode if you are currently using the ARCH transport mode. The ASYNC transport mode is superior to the ARCH transport mode in all respects, and is the new default transport mode.


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