This topic answers frequently asked questions about the backup and recovery features of and PolarDB for PostgreSQL (Compatible with Oracle).
Backup FAQ
-
Q: Is the total size of level-1 backups (snapshots) the sum of all individual backup sizes?
A: No. The total size of level-1 backups is not the sum of each backup's size. It is the physical storage size of level-1 backups (for example, 42.00 MB) displayed at the top of the backup management page, not the logical size of each backup set (for example, 2.32 GB) in the backup list.
-
Q: Why is the total size of level-1 backups smaller than the size of a single backup?
A: PolarDB reports two capacity metrics for level-1 backups: the logical size of each backup and the total physical size of all backups. PolarDB uses a snapshot chain mechanism for level-1 backups, where identical data blocks are stored only once. As a result, the total physical size is smaller than the total logical size and can even be smaller than the logical size of a single backup.
-
Q: What charges are associated with PolarDB backups?
A: You are charged for the storage space used by level-1 backups, level-2 backups, and log backups. The level-1 backup and log backup features are enabled by default, and a free storage quota is provided. The level-2 backup feature is disabled by default.
-
Q: How are fees for level-1 backups calculated?
A: The hourly fee is calculated as follows: [Total size of level-1 backups - (Database storage usage × 50%)] × Price per hour. For example, if the total size of level-1 backups for a PolarDB database is 700 GB and the database storage usage is 1,000 GB, the hourly fee is calculated as follows: [700 GB - 500 GB] x $0.000464 = $0.0928.
-
Q: Are manual backups supported only for level-1 backups?
A: Yes.
-
Q: What is the retention period for manual backups?
A: The retention period for a manual backup depends on the duration you set for Level-1 Backup in the Data Backup Retention settings of your backup policy.
-
Q: How do I view the size of a level-2 backup?
A: You can view the size of a level-2 backup on the Backups tab in the console.
Recovery FAQ
-
Q: If data is accidentally deleted or modified (for example, you delete a table, database, or cluster, or you overwrite or modify columns, rows, or data in a table), how do I recover it?
A: You can choose a recovery method based on your business needs. For more information, see Restore a cluster to a point in time and Restore a cluster from a backup set (snapshot).
-
Q: Can I customize the name for a restored table?
A: Yes.
-
Q: Can I perform a point-in-time recovery without a data backup?
A: No. A point-in-time recovery works by restoring a full backup created before the specified time to a new cluster, then applying incremental changes from physical logs to reach the target point in time.