Oracle database provides various backup and recovery strategies that help in maintaining data availability, minimizing data loss due to failures or disasters, and restoring data in case of data loss or application errors. In this answer, we will discuss the basic backup and recovery strategies in Oracle databases.
Backup Strategies: 1. Full backup: A full backup is a complete copy of the entire database, including all data files, control files, and redo logs. It provides the most comprehensive form of backup but is also the most time-consuming and resource-intensive method.
2. Incremental backup: An incremental backup involves backing up only the data that has changed since the last full or incremental backup. It reduces the backup time and space required for backup storage.
3. Differential backup: A differential backup is similar to an incremental backup but only includes the data that has changed since the last full backup. It requires less time and space for storage than full backup but more than incremental backup.
4. Online backup: An online backup is performed while the database is still running and accessible to users. It uses the database’s snapshot feature to take a point-in-time copy of the database. Online backup minimizes or eliminates downtime but can cause additional overhead on the system.
Recovery Strategies: 1. Complete recovery: A complete recovery involves restoring the entire database from a backup and applying all changes recorded in the redo logs since the backup was taken. It ensures that the database is restored to a consistent state.
2. Point-in-time recovery: Point-in-time recovery is a partial recovery that involves restoring the database to a specific time in the past. It involves restoring the database from a backup and applying selective redo log data to reach the desired point in time.
3. Media recovery: Media recovery is used to recover data files lost due to hardware or media failures. It involves restoring the lost data files from a backup and applying all changes recorded in the redo logs since the last backup.
4. Flashback recovery: Flashback recovery is similar to point-in-time recovery but uses Oracle’s flashback feature to restore the database to a previous state without the need for a traditional backup. It works by querying and recovering data from undo segments that store a history of data changes made to the database.
In summary, Oracle databases offer a variety of backup and recovery strategies to protect against data loss, minimize downtime, and ensure consistent data availability. The choice of strategy depends on the specific recovery requirements, system resources, and backup and recovery time windows. It is recommended to implement a combination of backup and recovery strategies to ensure optimal data protection and restore capabilities.