During database backup or restore processing, an error occurred because the specified device class is not defined.
If the database backup was started with the BACKUP DB command, the database backup is ended and server operation continues. If the database backup was triggered automatically, the backup stops and the server waits for the retry period to expire and then tries the database backup again. A database restore is terminated.
For database backup, make sure the specified device class is defined. For database restore processing, make sure the device class has a definition in a device configuration file that is pointed to in the server options file.