How does Oracle recover data after crashes?

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Mark Rosenthal2016-10-04 20:24:28

Oracle

Mark Rosenthal, 2016-10-04 20:24:28

Hello.
How is the database restored after an instance crash?
Heard confusion about undo/redo. Explain someone.

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2 answer(s)

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Eugene, 2016-10-04
@Lorien_Elf

Undo is needed for transaction rollback, redo is for instance disaster recovery.
If disaster recovery is required, then first the instance rolls forward the changes that were committed (commit) but were not written to disk. For this, online logs (online redo) are used. Next, the instance rolls back the changes that were not committed, for this, undo is used.
Details in the documentation.
https://docs.oracle.com/cd/E11882_01/server.112/e4...

A

Anton, 2016-10-04
@MoonMaster

Oracle database has a special RMAN tool. You can perform a backup restore provided that you have made a "restore point". You can read more details here