Oracle Distributed Systems

Distributed Backup and Recovery

If you arerecovering a database that participates in distributed transactions, you may need to coordinate your recovery with the other database instances. The good news is that if you perform complete recovery (the most common type of recovery), you have nothing to worry about.

Note

We are limiting our discussion to media recovery only, which is based on SCNs. Alternative methods, such as the import/export utilities, are not based on SCNs, and therefore you cannot coordinate them with distributed transactions in other databases.

Table 3.7 lists the possible recovery scenarios.

Table 3-7. Distributed Recovery Scenarios

Recovery Method	Impact on Databases Participating in Distributed Transactions
Restore from a cold backup	All other databases must also be restored to the same point in time.
Complete media recovery	No action required.
Incomplete media recovery	All other databases must also be restored to the same point in time.

As Table 3.7 indicates, the only recovery scenarios that impact other databases in the distributed environment are those in which the recovery is incomplete—that is, up to some time in the past. The obvious issue is that an incomplete recovery may result in data that is inconsistent globally because a distributed transaction may have been committed some time after the time to which you restore. Of course, if you can guarantee that no such transactions exist, you can recover to a time in the past without involving the other distributed databases. ...