The wal_backups directory is created on system startup whenever the system detects that the last condensation of the transaction log did not finish completely. Each subdirectory of wal_backups corresponds to one occurrence of such a situation.

The subdirectories may contain all or a subset of the following files: main.wal, main.wal.orig, location_map, location_map.orig, and the contents of the wal/pdts subdirectory. These are copies of the files found in the wal directory at startup.

The directory and its contents is a fail-safe mechanism that allows the database to be restored to its state following the last unfinished condensation of the transaction log. Normally the system handles such a situation automatically. If the automated mechanism fails, restoration must be performed manually with the assistance of Actian Support. Such a situation is unlikely.

Existence of the wal_backups directory simply means that the server terminated abnormally while the condensation of the transaction log was in process. If the system starts and works correctly, the wal_backups directory can be removed completely. If the system is unable to start, the data in wal_backups should be retained.