Teradata implements backups using changed block backups (CBB). With CBB, a system can run a full backup or only back up data blocks that have changed since a prior backup. This greatly reduces backup time and storage, at the cost of increased restore time. Restore time is increased because DSA has to read multiple backup save sets and construct the complete save set to restore. CBB allows cumulative or delta backups but restores must be full restores (For incremental backup and restore, see Using Incremental Restore to Maintain Your DR System). CBB backup is applicable to both standard (offline) backups and online archive.
- Databases and tables that have a very low change rate compared to table size
- Primary Partition Index (PPI) tables where changes are limited to one or few partitions
Three types of backups are available: full, delta, and cumulative.
The first backup must always be a Full backup. The full backup is the baseline for all further backups.
- A full backup archives all data from the specified objects. This backup takes the longest time to complete, and uses the most backup storage space. However, a full backup has the shortest restore time, since all data required to restore the objects is contained within a single backup save set.
- A delta backup archives only the data that has changed since the last backup. This backup completes in the shortest time and use the least storage space. However, a delta backup increases the time to restore the database, as it may add many backup save sets that must be processed before a set of objects can be fully restored.
- A cumulative backup archives the data that has changed since the last full backup. This backup type consolidates changes from multiple delta backups or cumulative backups before a full backup is run. A cumulative backup has a shorter database restore time than a series of delta backups, and takes less time and space than a full backup.
Guidelines for Backups
- Regardless of the type of backup performed, the dictionary information for all objects is fully backed up. This makes sure that all non-data objects and object definitions are fully recovered in the event of a restore from any point in time.
- In the event of a restore or analyze_validate, you select the backup save set corresponding to the point in time when you want the objects restored. This can be a full, delta, or cumulative backup save set. For a given restore point, the following save sets are processed, relative to the selected backup save set:
- Any delta backups after the most recent full or cumulative, and the selected restore point
- The most recent cumulative backup, if any. Only if newer than the full backup.
- The most recent full backup
In the event of an analyze_read, only the selected save set is analyzed.