Teradata ARC places change images in whatever journal table is defined. The table can be in the same database as the data tables or it can be in another database.
Each database can contain only one journal table, but any journal table and the data tables that use it can reside in the same or in different databases. Set up journaling to have a single journal table for all data tables in the Teradata Database, a separate journal table for each table within a database, or a combination of these two.
If a data table does not have fallback protection, Teradata ARC always writes its after images to another AMP (backup AMP) in the same cluster as the one containing the data being changed.
The following table shows where Teradata ARC writes journal change rows based on all the possible combinations of table protection and the specified journal option.
Journal Option | Fallback | Location of Change Data |
---|---|---|
After | Yes | Primary and Fallback AMPs |
Before | Yes | Primary and Fallback AMPs |
Dual After | Yes | Primary and Fallback AMPs |
Dual Before | Yes | Primary and Fallback AMPs |
After | No | Backup AMP |
Local After | No | Primary AMP |
Before | No | Primary AMP |
Dual After | No | Primary and Backup AMP |
Dual Before | No | Primary and Backup AMP |
If the dual option is specified, Teradata ARC writes an after-image on the primary and backup AMP. For a fallback table with a single after-image journal, Teradata ARC writes a journal row to the primary and fallback AMP. Teradata ARC also writes single before-images for nonfallback tables to the same processor as the data row being changed.