So, what's in a backup file?

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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
Log shipping in SQL Server 2005
Setting up log shipping using Management Studio
Checking the set up
Log shipping status report
Log shipping in SQL Backup
Using the CopyTool utility
3rd party backup applications
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
Integrated database verification
Database file relocation
Improved backup retention
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.
vdi error codes
Restore speed details
Help, my transaction log file is huge!
Mirror or log ship

During my days as a DBA, I frequently received backup files from my manager, with instructions to restore the contents.  Here's what I usually do to get a handle on things:

·Run RESTORE LABELONLY on the file

The information provided tells me if the backup file is the only one in a backup set, or if the backup file is part of a backup set.  The FamilyCount and FamilySequenceNumber columns provide this information.  Recall that a backup may be spread across multiple files.  In such situations, you would need all the files in order to restore the database successfully.


I use this to find out:


·the number of backups that are contained in the file.  A backup file may contain multiple backup sets.

·the backup type, whether if it's a full database backup, differential, log etc.

·the name of the database that was backed up.


I would only run this on a full database backup. Running this tells me the number of files that makes up the database, and the size of each file.  This allows me to know quickly if I have enough disk space to restore the database.


Can't we tell the size of the database from the backup file size?  No, if:


·the backup file contains multiple backup sets

·the database contains a lot of truncated data

·the database's tranaction log file contains mostly truncated data


In summary, there is a wealth of information you can retrieve from a backup file, using the RESTORE LABELONLY, RESTORE HEADERONLY and RESTORE FILELISTONLY commands.  See the Books Online documentation for these commands for more details.

Document history
6/27/2008    Initial release.    
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