Rolling Forward a Physical Standby Using Recover From Service Command in 12c
(Doc ID 1987763.1)
Last updated on AUGUST 16, 2021
Applies to:Oracle Database - Enterprise Edition - Version 18.104.22.168 and later
Information in this document applies to any platform.
Checked for relevance on 03-Dec-2019
Steps to perform for Rolling Forward a Physical Standby Database using RMAN Incremental Backup. (<Note:836986.1>)
Rolling Forward a Physical Standby Database Using the RECOVER FROM SERVICE Command
A standby database is a transactionally-consistent copy of the production database. It enables production Oracle database to survive disasters and data corruption. If the production database becomes unavailable because of a planned or an unplanned outage, Data Guard can switch a standby database to the production role, minimizing the downtime associated with the outage. Moreover, performance of production database can be improved by offloading resource-intensive backup and reporting operations to standby systems. As you can see, it’s always desirable to have standby database synchronized with the primary database.
Prior to 12c, in order to roll forward the standby database using incremental backups you would need to:
- Determine the necessary SCN of the standby
- Take an incremental backup on the primary starting from that SCN# of the standby database.
- Copy the incremental backup to the standby host
- Catalog the backups (copied from the primary) into the standby controlfile.
- Cancel managed recovery of the standby database and apply the incremental backup on the standby database.
- Create a control file for the standby database on the primary database.
- Mount the standby database with newly created standby control file.
- Start managed recovery of standby database.
In 12c, this procedure has been dramatically simplified. In 12c, you can use the RECOVER … FROM SERVICE command to synchronize the physical standby database with the primary database. This command does the following:
- Creates an incremental backup containing the changes to the primary database. All changes to data files on the primary database, beginning with the SCN in the standby data file header, are included in the incremental backup.
- Transfers the incremental backup over the network to the physical standby database.
- Applies the incremental backup to the physical standby database.
This results in rolling forward the standby datafiles to the same point-in-time as the primary. However, since the standby controlfile still contains old SCN values (lower than the SCN values of the standby datafiles) to complete the synchronization of the physical standby database, the standby control file needs to be refreshed.
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