Location of Change Data - TARA/ABU

Teradata Archive/Recovery Utility Reference

Product
TARA/ABU
Release Number
15.10
Language
English (United States)
Last Update
2018-10-07
dita:id
B035-2412
lifecycle
previous
Product Category
Teradata Tools and Utilities

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.

Table 10 shows where Teradata ARC writes journal change rows based on all the possible combinations of table protection and the specified journal option.

 

Table 10: Journal Change Row Location 

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.

Subtables

Teradata Database maintains journals in tables similar to data tables. Each journal table consists of active, saved and restored subtables. The active and saved subtables are the current journal. Teradata Archive/Recovery Utility appends change images from updates to a data table to the active subtable. Teradata ARC also writes rows marking a checkpoint on the journal to the active subtable.

Before archiving a journal table, use the CHECKPOINT statement with the SAVE option. The checkpoint operation logically terminates the active portion of the journal and appends it to the current saved portion. Archive this saved portion to the client or delete it from the Teradata Database.

When an archived journal is restored to the Teradata Database, Teradata ARC places change images in the restored subtable. For more efficient recovery operations, Teradata ARC always places the change images on the processor they apply to, instead of placing them on a backup processor. To delete a restored journal subtable, use the DELETE JOURNAL table statement.

Roll operations can use either the current journal or the restored journal. When the current journal is specified, Teradata ARC automatically uses both the active and saved subtables of the journal table.