Canceling Tape Change Request Prevents Restore Operation

• Microsoft Windows NT Workstation version 3.5
• Microsoft Windows NT Server version 3.5

SYMPTOMS

When a backup set transaction exceeds the first backup tape's capacity, Windows NT Backup (NTBACKUP.EXE) asks you to insert a second backup tape. If you cancel this request, any future attempts to restore files from the tape will fail when the restore operation requests the second tape (which was never created).

CAUSE

Since Windows NT Backup does not know how many volumes, directories and files will be backed up in a set when the backup begins, a special indicator at the end of the backup set shows that there is no more backup data associated with the set. The indicator also contains information that is not available until the backup is completed, such as the number of corrupt files backed up and information about the on tape catalog (OTC). OTCs are designed to store information about a tape family's data sets, and the objects in a given data set, in a readily accessible location. If the OTC is missing the standard restore action fails because it relies on the OTC to restore data.

WORKAROUND

To work around this problem run NTBACKUP with the /MISSINGTAPE parameter.

The /MISSINGTAPE parameter causes Windows NT Backup to scan the entire family of tapes in order to get data set information. For more information on this parameter, see the Windows NT Backup help file.

MORE INFORMATION

The OTC system is slower than a disk based catalog system because the tape has to be scanned for the OTC, and the contents have to be read. However, the OTC system is more convenient because it always accompanies the data it refers to and does not occupy the fixed disk space required by disk based catalogs.