Thursday, May 24, 2012

Implement Programming Objects: Write automation scripts

(This is part of the Study Guide series, 70-464)

Microsoft’s Measured Skill description: This objective may include but is not limited to: automate backup testing; shrink file; check index fragmentation; archive data; run an SQL Server Integration Services (SSIS) job; check disk space; automate backups

What I see:
·         automate backup testing
·         shrink file
·         check index fragmentation
·         archive data
·         run an SSIS job
·         check disk space
·         automate backups

Automate Backup Testing
                I wrote a script to do this.  Basically it takes a backup and restores it as a stand-alone database and then runs DBCC CHECKDB against the restored database.  It’ll report the results of the DBCC CHECKDB and then drop the database.  This script can be found here on my GitHub SQLSalt reposity.

Shrink File
                I’m actually a bit surprised that Microsoft put this in the objectives.  It is not advisable to consistently shrink database files, as this operation can cause extreme data fragmentation.  For my testing purposes, I altered the size of my MeasureMySkills database files to 10000 MB each to show the drastic differences in file shrinkage.  If you want to get database file space usage statistics for your current database, you could execute the following query:

use MeasureMySkills;

;with DatabaseFileInfo as
              db_name(database_id) as database_name,
              name as db_file_name,
              size * 8 as total_size_kb,
              fileproperty(name, 'SpaceUsed') * 8 as space_used_kb
       from sys.master_files
       where database_id = db_id()
       total_size_kb - space_used_kb as free_space_kb,
       cast(space_used_kb * 1.0 / total_size_kb * 100.0 as decimal(5, 2))
              as percent_used
from DatabaseFileInfo

This will let you know how much space is actually being used, and how much is allocated.  If for some reason you want to shrink a database file, you could do the following (I’m using my MeasureMySkills database in the following example):

-- shrink my data file
dbcc shrinkfile('MeasureMySkills', 0);
-- shrink my log file
dbcc shrinkfile('MeasureMySkills_log', 0);

Then re-running the database file space usage stats query from before, you should see regained space (for the data file, close to 100% usage and for the log file it will be bound by VLFs so your results may vary).  You can automate this process by creating a Maintenance Plan and utilizing a Shrink Database Task.  You could also use schedule a job to check a database’s file space usage, and if it drops below a certain threshold it could shrink database files (also possible cumulatively through DBCC SHRINKDATABASE).  Again, this is not recommended in production.  It is better to make an educated calculation of data scalability and create an appropriately sized database.  There’s a good saying that if space was once used by a database (i.e. it auto grew, or more space was allocated for a reason) then it will probably need it again.  Drive space is cheap; poor performance and unwieldy fragmentation can be expensive.

Check Index Fragmentation
                I wrote a script that can be found on my GitHub SQLSalt repository that basically gets a summary of index fragmentation for a particular database with a minimum page threshold.  It utilizes the sys.dm_db_index_physical_stats DMV with a join on the sys.indexes catalog view.  Running it against AdventureWorks2012:

use AdventureWorks2012;

@page_count_min bigint = 1000;

       db_name(ps.database_id) as database_name,
       object_name(ps.object_id) as object_name, as index_name,
from sys.dm_db_index_physical_stats
) ps
inner join sys.indexes i
on ps.object_id = i.object_id
and ps.index_id = i.index_id
where ps.page_count >= @page_count_min
order by ps.avg_fragmentation_in_percent desc;

Archive Data
                Archiving data can be done a few ways.  As far as automation goes, it could be something as simple as a SQL Server Agent job run daily (or weekly, or monthly) to copy data from an active table to an archive table.  This can also be done through PowerShell.  It is as simple as a DELETE FROM… OUTPUT INTO … statement.

Run an SSIS Job
                Again, running a SQL Server Agent job with an SSIS job step can be down through a SQL Server Agent schedule.

Check Disk Space
                Checking disk space can be something that is done by scheduling a job that makes a call to the master.sys.xp_fixeddrives extended stored procedure.  This will return a row per logical drive and the remaining space in MB.  If this is below a particular threshold, then use DBMail to send an email, log it to the event log, or take whatever action you find appropriate.  Likewise, you can setup a WMI alert within SQL Server Agent with a WQL query to notify this information.

Automate Backups
                This is one of the basic steps of automation.  It is typical for a DBA to create either a Maintenance Plan to do full, differential, and transaction log backups regularly and on a schedule, or create each individual SQL Server Agent job to accomplish the same tasks.  These are simple BACKUP DATABASE/LOG statements, and it is also worth noting that these backups should be tested for integrity.



If there are any comments, questions, issues, or suggestions please feel free to leave a comment below or email me at

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