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This
document describes how SQL Backup performs backups, to aid readers
in understanding the similarities between a backup performed using
SQL Backup and one performed using SQL Server.
Native SQL Server backup
When you perform a backup using SQL Server, you issue s a
T-SQL BACKUP
command
to SQL Server, with the relevant options set e.g. DISK,
DIFFERENTIAL
etc.
E.g.
| BACKUP DATABASE pubs TO DISK = 'E:\Backups\pubs.sqb' WITH
DIFFERENTIAL |
SQL Server then generates the relevant backup data and writes them
out to disk or tape.
SQL Backup backup
When you perform a backup using SQL Backup, SQL Backup
issues a T-SQL BACKUP command to SQL Server, with the relevant
options set e.g. DISK,
DIFFERENTIAL
etc.
The command is almost similar to that used when using native SQL
Server backup. One difference is that instead of the DISK
option,
SQL Backup uses the VIRTUAL_DEVICE
option
e.g.
| BACKUP DATABASE pubs TO VIRTUAL_DEVICE = '<some unique
value>' WITH DIFFERENTIAL |
SQL Server then generates the relevant backup data, but does not
write it out to disk or tape. Instead, it informs SQL Backup where
the backup data can be found. SQL Backup then compresses this data,
optionally encrypts it, and writes it out to disk.
Points to note:
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The
backup data is generated by SQL Server in all cases. SQL Backup
does not generate any backup data.
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The
backup data that is generated by SQL Server is identical (aside
from block sizing issues) in both the above cases.
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Because
the backup data is identical, it is possible for SQL Backup to
convert its compressed files to native SQL Server backup files,
using either the CONVERT
command
or the sqb2mtf utility. These converted files can then be restored
using native SQL Server RESTORE
commands.
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Because
the backup data is identical, you can perform the same tasks using
SQL Backup as you would using native SQL Server backups e.g.
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1.
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perform
full, differential, transaction log, partial, filegroup backups and
restores, STOPAT,
PAGE
restores
etc, as long as SQL Backup supports the required SQL Server option
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2.
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run
RESTORE
VERIFYONLY,
RESTORE
HEADERONLY,
RESTORE
FILELISTONLY commands
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3.
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backup
a SQL Server 2000 database and restore the database on a SQL Server
2005 or SQL Server 2008 instance
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For further details, see this document
Document history
| 12/3/2008 | Initial release. |
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