Leveraging Storage Spaces Direct for SQL Server High Availability
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When a failure occurs you need to act quickly to possibly restore your database. When you are performing both full and transaction log backups there are multiple files that will need to be restored and therefore your restore script could get quite long and tedious to write. When using Enterprise Manager or SQL Server Management Studio the GUI gives you the list of files that should be restored, but what if you need to do this manually or you would rather have a script to perform the restore process instead of using the GUI. How can you easily generate the restore script?
For every backup that occurs in SQL Server an entry is made into the system tables that reside in the MSDB database. This includes both native SQL Server backups as well as backups that occur using third party tools. These tables that hold this backup information are:
- backupfile -- contains one row for each data file or log file backed up
- backupmediafamily -- contains one row for each media family
- backupmediaset -- contains one row for each backup media set
- backupset -- contains one row for each backup set
By querying these tables you can determine when the last backups occurred, what type of backups occurred and also where the files were physically written. These tables on their own are not all that helpful, but when you combine the contents from each of these tables you can piece together your entire backup string and create an easy to use restore script.
The following is a simple script that queries the backupset and backupmediafamily tables. This script assumes that the backup files are being written to disk and not directly to tape, but this script can be modified to include these checks as well. The idea behind this is that you will want to always restore your latest backup set, which is probably the set of files you still have on disk. In most cases when a failure occurs or someone accidentally deleted important data you will probably only need to go back to the latest full backup and the appropriate transaction logs.
Here is the script, the only parameter that needs to be set is the database that you want to retrieve backup information for. The process will then find the latest Full backup and all transaction log backups that have occurred after this full backup. The last step is to create a WITH RECOVERY command that puts the database online and makes it accesible.
DECLARE @databaseName sysname DECLARE @backupStartDate datetime DECLARE @backup_set_id_start INT DECLARE @backup_set_id_end INT -- set database to be used SET @databaseName = 'enterDatabaseNameHere' SELECT @backup_set_id_start = MAX(backup_set_id) FROM msdb.dbo.backupset WHERE database_name = @databaseName AND type = 'D' SELECT @backup_set_id_end = MIN(backup_set_id) FROM msdb.dbo.backupset WHERE database_name = @databaseName AND type = 'D' AND backup_set_id > @backup_set_id_start IF @backup_set_id_end IS NULL SET @backup_set_id_end = 999999999 SELECT backup_set_id, 'RESTORE DATABASE ' + @databaseName + ' FROM DISK = ''' + mf.physical_device_name + ''' WITH NORECOVERY' FROM msdb.dbo.backupset b, msdb.dbo.backupmediafamily mf WHERE b.media_set_id = mf.media_set_id AND b.database_name = @databaseName AND b.backup_set_id = @backup_set_id_start UNION SELECT backup_set_id, 'RESTORE LOG ' + @databaseName + ' FROM DISK = ''' + mf.physical_device_name + ''' WITH NORECOVERY' FROM msdb.dbo.backupset b, msdb.dbo.backupmediafamily mf WHERE b.media_set_id = mf.media_set_id AND b.database_name = @databaseName AND b.backup_set_id >= @backup_set_id_start AND b.backup_set_id < @backup_set_id_end AND b.type = 'L' UNION SELECT 999999999 AS backup_set_id, 'RESTORE DATABASE ' + @databaseName + ' WITH RECOVERY' ORDER BY backup_set_id
When the above is run for database "DButil" the following result set is generated. This generated 4 lines of code for this database. The T-SQL code in column (no column name) could then be copied and pasted into a query window to be executed to do the restore or it could be modified to only include the transaction log files you need, especially if you needed to do a point in time recovery.
Line 1 is the full backup, lines 2 and 3 are the transaction log backups and line 4 is the WITH RECOVERY option which takes the database out of the loading state and makes the database accessible.
This is a very basic process of finding the latest full backup and all of the transaction log backups. It does not take into consideration additional backups that are written to the same file or differential backups. There are several tweaks that could be made to further enhance this script, but hopefully this gives you a starting point to automate your restore scripts instead of having to rely on the GUI to provide this data or having to manually type each command for every single backup.
- Take a look at other backup and restore tips
- Start with this base script and add additional functionally to meet your needs. If you create a better version, please send to [email protected] so we can make this avaiable to the entire MSSQLTips.com community.
- Turn this script into a stored procedure that takes the database name as a parameter
- Setup a process where this runs on a set schedule and automatically generates the script for you. This way if there is a need to do a fast recovery the restore script is already available.
- Check out this updated script by Glynne Smith from the MSSQLTips community. This update handles a single backup striped across multiple files. Thanks Glynne for the update.
- Here is another version from Chris Gelhaus. This updated version handles differential backups as well as multiple backups written to the same file. Thanks Chris.
Last Update: 2007-05-14
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