Consider the following scenario. You install Microsoft SQL Server on a volume. You use a Volume Shadow Copy Service (VSS) application to back up files on the volume. In this scenario, SQL Server records a backup operation in the backupset history table. This problem occurs even if you did not actually back up the database files of SQL Server.
Note The NTBackup.exe utility is a
VSS application.
This problem occurs because VSS calls the
SQLWriter service or the Microsoft SQL Server Desktop Engine (MSDE) writer.
Microsoft
has confirmed that this is a problem in the Microsoft products that are listed
in the "Applies to" section.
Description of the MSDE writer and the SQLWriter service
The MSDE writer is included in the VSS framework in Windows XP and
in Windows Server 2003. VSS uses the MSDE writer to back up
SQL Server 2000 databases. The SQLWriter service is
installed when you install SQL Server 2005. VSS uses the SQLWriter service to back up both
SQL Server 2005 databases
and SQL Server 2000
databases.
How VSS performs a backup operation
When VSS performs a backup operation on a volume, VSS calls
all writers that have data on the volume. This makes sure that the backup is
valid. When VSS calls the SQLWriter service or the MSDE writer, the
SQLWriter service or the MSDE writer inserts a record into the backupset
history table. This
record shows that a backup operation was
performed. However, the SQLWriter service or the MSDE writer cannot determine
whether the files that VSS backed up are
database files.
Precautions to take if you use the entries in the backupset history table for data recovery
If you want to use entries in the backupset history table for data
recovery, you must verify that the entries represent actual database backup
operations.
How to verify that an entry represents an actual database backup operation
To do this, run the following statement.
USE msdb
GO
SELECT server_name, database_name, backup_start_date, is_snapshot, database_backup_lsn
FROM backupset
In the result, notice the database_backup_lsn column and the
is_snapshot column. An entry that represents an actual database backup
operation has the following characteristics:
- The value of the database_backup_lsn column is not
0.
- The value of the is_snapshot column is 0.
For more information about the SQL Writer service, visit the
following Microsoft Developer Network (MSDN) Web site:
For
more information about the backupset history table, visit the following MSDN
Web site: