Oracle Database Recovery Strategies
1. Key Concepts
- Complete Recovery
- Incomplete Recovery
- Point-in-Time Recovery
- Flashback Technology
2. Complete Recovery
Complete Recovery involves restoring the database to its most recent state using backups and redo logs. This strategy ensures that all committed transactions are recovered, and the database is brought back to its latest consistent state. Complete Recovery is typically used after a major failure or corruption.
Example: Imagine a complete recovery as restoring a computer to its factory settings using a backup. All data and settings are restored to their most recent state, ensuring no data is lost.
3. Incomplete Recovery
Incomplete Recovery involves restoring the database to a state before a specific point in time. This strategy is used when certain transactions need to be undone or when the database is corrupted beyond the latest backup. Incomplete Recovery can be performed to a specific time, SCN (System Change Number), or log sequence number.
Example: Think of incomplete recovery as rewinding a movie to a specific scene. You can go back to a particular point in time, but you lose everything that happened after that point.
4. Point-in-Time Recovery
Point-in-Time Recovery (PITR) allows the database to be restored to a specific point in time within a defined window. This strategy is useful for recovering from logical errors, such as accidental data deletion or update. PITR uses backups, archived redo logs, and possibly incremental backups to achieve the desired recovery point.
Example: Consider PITR as restoring a document to a previous version in a version control system. You can select a specific version of the document, and all changes made after that point are undone.
5. Flashback Technology
Flashback Technology allows the database to be restored to a previous state without requiring a full backup and restore process. This technology uses undo data and other internal mechanisms to quickly revert the database to a previous state. Flashback Database, Flashback Table, and Flashback Drop are common tools within this technology.
Example: Think of Flashback Technology as using a "time machine" to go back to a previous state of the database. This allows you to quickly undo changes without the need for extensive recovery processes.
By understanding these key recovery strategies, you can effectively manage and restore your Oracle Database 12c in various failure scenarios, ensuring data integrity and availability.