4. PROACTIVELY TUNING SQL SERVER PERFORMANCE WITH POWERSHELL

Now that you’ve seen some of the building blocks of PowerShell it’s time to see how easy it is to combine all this together and build some more functional scripts. Remember, everything can be broken back down to cmdlets and variables; so if you find that your script is getting too complex and difficult to work with, break it back down and build it back up.

In this next section we will examine some scripts that can be used to help with SQL Server tuning as we look at index maintenance, managing disk space, and scripting out DDL data.

4.1 Index Maintenance

To ensure maximum performance is obtained, index maintenance is an important job when managing a SQL Server. Traditionally, a DBA may have written some T-SQL to perform index maintenance, but this is not a simple task and one probably not best suited to T-SQL because of the procedural nature of the task. PowerShell offers an elegant solution to index maintenance in collaboration with the SQL Server SMO library. The following script shows how a fairly comprehensive index maintenance routine can be performed in just a few lines of PowerShell. The script iterates through all the indexes within all the tables of a user database, and based on the fragmentation level of the index performs one of three tasks (code file: PS_ManageFragmentation01.PS1):

• If the index is less than 5% fragmented, then do nothing because the performance benefit of maintaining the index on this occurrence is negligible.
• If the index is between 5% and 30% fragmented, then perform an index reorganization.
• If the index is greater than 30% fragmented, then perform an index rebuild.

[string] $ServerName = $args[0]
[string] $TargetDatabaseName = $args[1]
 
[Reflection.Assembly]::LoadWithPartialName("Microsoft.SqlServer.Smo") | out-null
$server = New-Object Microsoft.SqlServer.Management.Smo.Server $ServerName
$targetDB = $server.Databases[$targetDatabaseName]
 
foreach ($table in $targetDB.Tables)
{
       foreach($index in $table.Indexes)
       {
             $fragmentation = $index.EnumFragmentation()
             $averageFragmentation = $fragmentation.Rows[0].AverageFragmentation
             
             if($averageFragmentation -lt .05)
             {
                    continue
             }
              
             if($averageFragmentation -ge .05 -and $averageFragmentation -lt .3)
             {
                    $index.Reorganize()
                    continue
             }
              
             $index.Rebuild()
         }
}

4.2 Managing Disk Space Utilization of Backups

Working with the file system is very straightforward with PowerShell. In the following example, I have created a small script that removes transaction log backups that are older than two days, differential backups that are older than eight days, and full backups that are older than 91 days. By splitting the Get-ChildItem query into three queries based on file extension and last write time, it was simply a matter of setting the number of days to subtract from the current date to define the retention period for each backup type (code file: PS_DeleteOldBackups01.PS1):

Get-ChildItem .\Backups -include *.trn -recurse '
      | Where-Object { $_.lastwritetime -lt (Get-Date).AddDays(-2) } '
      | Remove-Item
 
Get-ChildItem .\Backups -include *.dif -recurse '
      | Where-Object { $_.lastwritetime -lt (Get-Date).AddDays(-8) } '
      | Remove-Item
 
Get-ChildItem .\Backups -include *.bak -recurse '
      | Where-Object { $_.lastwritetime -lt (Get-Date).AddDays(-91) } '
      | Remove-Item