The applier

The applier reads data from the control table created by the stager. It begins processing the required transaction and updates the control table to show that this transaction is in process. Next, it operates on each successive log record, row by row, until the transaction commits.

All updates to the control table occur in the same transaction as the log record modification. This allows all work to be completed or undone as a single unit, maintaining integrity at all times. If an error occurs, the transaction is rolled back and the error is recorded in the control table entry for this transaction.

When data is being restored and the DBA has elected to include a logical restore, two additional work columns and an index are added to the destination table. These columns contain the original rowid and original part number. These columns provide a unique key which identifies the location of the row on the original source archive. To control the storage of the index, use the SET WORKSPACE command (see The SET statement). Otherwise, the index is stored in the same space as the table.

After the applier has finished and the restore is complete, these columns, and any indexes created on them, are dropped from the destination table.