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.