Search booster
Database Window - Database – Create/Delete search booster (in the database window)
The search booster consists of a pair of additional files attached to a database. They consume about 50 bytes per game (so they can be fairly large). But it speeds up the search for specific games and positions considerably. The booster files have the ending .CBB and CBO and can be deleted from your hard disk if no longer required.
The program will offer to create a search booster for a large database which doesn't have one. You can also use this command to delete the booster files.