In the event system crashed, it may not be possible to start up the database. This is likely because the database files may be corrupted or in an inconsistent state.

The “.log” file should allow HSQLDB to redo database changes that are not yet through a checkpoint. However, the “.data” file may be corrupted. In such case delete the “.data” file. HSQLDB should be able to restore from the “.backup” file. Together with the “.log” it should be able to recover everything.