Database Backup History – Back to Basics
Back in late December of 2015, a challenge of sorts was issued by Tim Ford (twitter) to write a blog post each month on a SQL Server Basic. Some have hash-tagged this as #backtobasics. Here is the link to that challenge sent via tweet.
I did not officially accept the challenge. Was an official acceptance required? I don’t know. I do know that I think it is a good challenge and that I intend to participate in the challenge. I hope I can meet the requirements and keep the posts to “basics”. Let’s hope this post holds up to the intent of the challenge.
With this being another installment in a monthly series, here is a link to review the other posts in the series – back to basics. Reviewing that link, you can probably tell I am a bit behind in the monthly series.
Database Backup History
As a data professional, there is little to no doubt that one of the most important tasks is to ensure the data is backed up regularly. We do this in preparation for several reasons. Whether it be to be able to recover in the event of a problem or to compare yesterdays data to how it looks today, the backup is done.
When doing a backup, how often do you report on the backup success? How frequently do you refer to the backup history to compare multiple runs or even generate reports for interested parties? The fact of the matter is that this history should be referenced on a routine basis to generate reports that should be read and not ignored.
Right about here you may be asking yourself why would somebody generate reports on the backups. After all, the job succeeds or fails and you respond appropriately to that, right? Does one really need to generate a report about the success of the backup job? Well, that is for you to decide. I would say it wouldn’t hurt to generate a report about the success rate of your backups. Management often likes to see reports concerning important processes. That said, that is not the reporting that I am referencing here.
The reporting I believe is useful in this case is indeed related to the historical information of your backups, but it is less about the success of the job and so forth. Of great benefit from the backup history data is the information on frequency of backup and also the size of the backup. These pieces of information can be somewhat useful when looking to forecast data growth. That is one example of a possible report when working with the backup history data that is stored.
Let’s take a look at a query that will help retrieve some of this backup history data.
DECLARE @SQLVer SQL_VARIANT
, @DBName VARCHAR(128)
, @NumDays SMALLINT
, @SQL VARCHAR(1024)
, @WhereClause VARCHAR(256);
SET @DBName = NULL;
SET @NumDays = 10000;
SET @SQLVer = CONVERT(INTEGER, PARSENAME(CONVERT(VARCHAR(20), SERVERPROPERTY('ProductVersion')),
SET @WhereClause = 'WHERE a.type IN (''D'',''I'')
AND a.backup_start_date > GETDATE()- ' + CAST(@NumDays AS VARCHAR) + '';
IF @DBName IS NOT NULL
SET @WhereClause = @WhereClause + '
AND a.database_name = ''' + @DBName + '''';
SET @SQL = '
,datediff(second,a.backup_start_date,a.backup_finish_date)/60.0 as DurationMinute
,b.physical_device_name AS BackupPath
,a.backup_size/1024/1024 AS BackupSizeMB
,' + CASE WHEN @SQLVer < 10 THEN '0'
END + ' AS CompressedBackMB
FROM msdb.dbo.backupset a
INNER JOIN msdb.dbo.backupmediafamily b
ON a.media_set_id = b.media_set_id
' + @WhereClause + '
ORDER BY a.database_name,a.backup_start_date;';
Off the top, yes the script uses dynamic sql. I use dynamic sql because I use this script on multiple versions of SQL Server. One of the data points I gather in this script is the compressed backup size. That attribute is not available in SQL 2005. Due to that, and not wanting to maintain multiple scripts, I use the dynamic sql to account for that missing column.
I have also set the script to accept a database name parameter. If a name is provided, then only the backup history for that database is returned. If the parameter is left NULL, then the backup history for all databases will be returned. Additionally, I added a number of days parameter to limit the scope of the report to a specific range of days.
Among the data points returned in this script, you will note there is the duration of the backup, the date, and even the size of the backup. All of these attributes can help me to forecast future storage requirements both for the backup storage as well as for the data volume. Additionally, by knowing the duration of the backup and the trend of that duration, I can adjust maintenance schedules accordingly.
In this particular script, I only retrieve the backup history for two backup types: FULL and DIFFERENTIAL. A small adjustment can be made to include other backup types if necessary. The line to change is:
SET @WhereClause = 'WHERE a.type IN (''D'',''I'')
Other possible values for backups are:
- D = Database
- I = Differential database
- L = Log
- F = File or filegroup
- G =Differential file
- P = Partial
- Q = Differential partial
If you are interested in learning more about backup information, you can read this msdn article – here.
I have provided a quick example of how to retrieve pertinent backup history information. This information can be used to assist in forecasting storage requirements as well as assist in the job scheduling as backup jobs begin to run longer and longer as the data gets larger and larger.
For a related article, check out this article on how to retrieve the restore history from the msdb database.