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Test: A full backup does not contain deleted data

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Introduction
Recovery models
Main backup types
Backing up the database files by copying
The transaction log
Transaction log restore sequence
Log sequence numbers
Truncating and shrinking the transaction log
Backing up the tail
Inside the transaction log
So, what's in a backup file?
Test: A full backup does not contain deleted data
Verifying backup files
Verifying backup files on a budget
Cumulative backups
Recovering individual tables
Backup and restore history details
Backup reads and writes
Speeding up backups
Backup speed details
Speeding up restores
Restore state affects speed too
Backup and restore rights
Log shipping
Log shipping in SQL Server 2000
Setting up log shipping using Enterprise Manager
Checking the set up
Failover
Log shipping in SQL Server 2005
Setting up log shipping using Management Studio
Checking the set up
Log shipping status report
Failover
Log shipping in SQL Backup
Using the CopyTool utility
Failover
3rd party backup applications
VDI
VDI versions
VDI errors
SQL Backup - beyond compression
Restoring a chain of transaction log backups
Restoring to the latest possible state
Backing up multiple databases
Backup retention
Making a copy of the backup file
Backup file naming conventions
Restoring the latest backup set
Network resilience
Encryption
Integrated database verification
Database file relocation
Improved backup retention
RESTORE HELP
High-availability group support
Common SQL Backup issues
Installation checklist
Setting up rights
Configuring service rights
Backup data
Hanging issues
Common backup and restore errors
Error 3201 - when performing a backup to a network share
Full database backup file is larger than database size
Error 3205 - Too many backup devices specified for backup or restore
Error 4305 - an earlier transaction log backup is required
Bringing a database that is in recovery or read-only mode online
Using bulk-logged recovery model but transaction log backup is still large
Error 14274 - unable to delete SQL Server Agent job
Error messages when restoring from different versions of SQL Server.
Pending
vdi error codes
Restore speed details
Help, my transaction log file is huge!
Mirror or log ship



Run the following script:

CREATE DATABASE sizetest
GO
USE sizetest
GO
CREATE TABLE data (col1 char(8000))
INSERT INTO data VALUES ('A')
INSERT INTO data SELECT * FROM data
INSERT INTO data SELECT * FROM data
INSERT INTO data SELECT * FROM data
INSERT INTO data SELECT * FROM data
INSERT INTO data SELECT * FROM data
INSERT INTO data SELECT * FROM data
INSERT INTO data SELECT * FROM data
INSERT INTO data SELECT * FROM data
INSERT INTO data SELECT * FROM data
GO
BACKUP DATABASE sizetest TO DISK = 'e:\temp\sizetest_1.bak'
DROP TABLE data
BACKUP DATABASE sizetest TO DISK = 'e:\temp\sizetest_2.bak'

The first backup generates the following output:

Processed 664 pages for database 'sizetest', file 'sizetest' on file 2.
Processed 2 pages for database 'sizetest', file 'sizetest_log' on file 2.
BACKUP DATABASE successfully processed 666 pages in 0.549 seconds (9.924 MB/sec).

while the second backup generates the following output:

Processed 152 pages for database 'sizetest', file 'sizetest' on file 2.
Processed 4 pages for database 'sizetest', file 'sizetest_log' on file 2.
BACKUP DATABASE successfully processed 156 pages in 0.221 seconds (5.782 MB/sec).

Note that the second backup actually backed up less pages (156), since we deleted all the data.  The first backup file size is 7.7 MB, while the second is 2.6 MB.  If you restore the database using the second backup file, your database files would still require the same amount of free space as the first backup (~ 9 MB), because that was the size of the database files during the time of backup.

If you want to reduce the size of the database files in this case, you would need to run DBCC SHRINKDATABASE, DBCC SHRINKFILE or set the database to auto-shrink.  Note that there are caveats to doing this if the deletion and growth is normal for the database.  Constantly shrinking and growing the database file will cause it to fragment on the disk, imposes a disk and processor overhead during the shrinking process, and a disk overhead again during the growth process.




Document history
6/27/2008    Initial release.    
 
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