[ORACLE] Mechanics of Instance and Crash Recovery
1. Rolling forward to recover data that has not been recorded in the datafiles, yet has been recorded in the online redo log, including changes to undo blocks. This phase is called cache recovery.
2. Opening the database. Instead of waiting for all transactions to be rolled back before making the database available, Oracle allows the database to be opened as soon as cache recovery is complete. Any data that is not locked by unrecovered transactions is immediately available.
3. Marking all transactions systemwide that were active at the time of failure as DEAD and marking the rollback or undo segments containing these transactions as PARTLY AVAILABLE.
4. Rolling back dead transactions as part of SMON recovery. This phase is called transaction recovery.
5. Resolving any pending distributed transactions undergoing a two-phase commit at the time of the instance failure.
6. As new transactions encounter rows locked by dead transactions, they can automatically roll back the dead transaction to release the locks. If you are using Fast-Start Recovery, then only the data block is immediately rolled back, as opposed to the entire transaction.
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