Performing Media Recovery in a Distributed Environment: Scenario

How you perform media recovery depends on whether your database participates in a distributed database system. The Oracle distributed database architecture is autonomous. Therefore, depending on the type of recovery operation selected for a single damaged database, you may have to coordinate recovery operations globally among all databases in the distributed system.

Table 19-2, "Recovery Operations in a Distributed Database Environment" summarizes different types of recovery operations and whether coordination among nodes of a distributed database system is required.

Table 19-2 Recovery Operations in a Distributed Database Environment

If you are . . .	Then . . .
Restoring a whole backup for a database that was never accessed from a remote node	Use non-coordinated, autonomous database recovery.
Restoring a whole backup for a database that was accessed by a remote node for a database in `NOARCHIVELOG` mode	Shut down all databases and restore them using the same coordinated full backup.
Performing complete media recovery of one or more databases in a distributed database	Use non-coordinated, autonomous database recovery.
Performing incomplete media recovery of a database that was never accessed by a remote node	Use non-coordinated, autonomous database recovery.
Performing incomplete media recovery of a database that was accessed by a remote node	Use coordinated, incomplete recovery to the same global point in time for all databases in the distributed system.

Coordinating Time-Based and Change-Based Distributed Database Recovery

If one node in a distributed database requires recovery to a past time, it is often necessary to recover all other nodes in the system to the same point in time to preserve global data consistency. This operation is called coordinated, time-based, distributed database recovery. The following tasks should be performed with the standard procedures of time-based and change-based recovery described in this chapter.

Recover the database that requires the recovery operation using time-based recovery. For example, if a database needs to be recovered because of a media failure, then recover this database first using time-based recovery. Do not recover the other databases at this point.
After you have recovered the database and opened it with the RESETLOGS option, search the alert_SID.log of the database for the RESETLOGS message.

If the message is, "RESETLOGS after complete recovery through change xxx", then you have applied all the changes in the database and performed complete recovery. Do not recover any of the other databases in the distributed system, or you will unnecessarily remove changes in them. Recovery is complete.

If the message is, "RESETLOGS after incomplete recovery UNTIL CHANGE xxx", then you have successfully performed an incomplete recovery. Record the change number from the message and proceed to the next step.
Recover all other databases in the distributed database system using change-based recovery, specifying the change number (SCN) from Step 2.