Database window: Maintenance – Check Integrity
Databases can sometimes become corrupted. The files can be damaged by viruses, a damaged disk surface, power surges or failures during a write operation, etc. Also, file operations outside of ChessBase may cause problems.
The integrity test checks a database for errors. It will also attempt to repair any damage it finds. Since this is a delicate operation you should definitely make a backup of the files before you use the integrity check.