Category Archives: DBA

First day on the job as a DBA

So I’m starting out a new job today and figured I would write up a checklist of things I needed to complete to own the Databases I have to start managing.

  1.  Get a list of Servers I’ll be managing/owning.  This can be done with a script or just by the company letting you know which ones.  It’s not a bad idea using the script to find some other servers that might be out there that the company was not aware of.  Pinal Dave has a good example of this on his blog.
  2. Run the SP_Blitz script from Brent Ozar (blog | Twitter) this is full of all sorts of good tidbits on what you need to look at for a server.  Check out the blog post in the link above and it will fill you in on the many great things this script can do for you.
  3. Get a DBA database created on each server.  I typically use this to house all sorts of maintenance type things and monitoring and alerting.  Every DBA should have a DB to call their own.
  4. Create the server side trace.  Years ago back in SQL 2000 I wrote a server side profiler trace that would run all the time and store the contents down to a table that I could later review to watch performance of queries hitting the DB.  Over the year’s fellow DBA’s have made updates to the script and made it better and it’s one of those key things I still depend on now.  I should get a future blog post out on this one.
  5. Create perfmon counters.  I store perfmon counters down to a db through an odbc connection in perfmon.  This way I can use a custom set of reports I’ve created to report trends on my server/db performance.  This also gets me started on my benchmark and knowing where things are when I started.  I should have some future blogs on this.
  6.  Install SSMS tools pack.  No one should go without this tool.   Saved me more times than I can count I would suggest it to everyone.
  7. Check the backups/backup schedule.  Blitz script is going to tell me some of this but I want to make a point to check with the business as to what the backups schedule is and make sure that matches what is really happening.
  8. Check the security model and who has access to the DB.  Again Blitz script might tell me some of this but I’ll make it a point to make sure something like domain admins don’t have full rights to the db and there are 100 people in domain admins (yes I’ve seen this before).

This is all the primary things I could come up with on day 1.  There’s still more items I’m sure but these are key and all have to be in place so I can continue moving forward from here I should have a good base to work with.

If you have other suggestions  let me know!

T-SQL Tuesday, Why are DBA skills necessary?

I wanted to add my thoughts on this month’s T-SQL Tuesday.  Haven’t heard about T-SQL Tuesday yet? Here are the details on it.

What is T-SQL Tuesday?

If you haven’t seen it yet, T-SQL Tuesday is the brain-child of fellow-MVP Adam Machanic (blog|twitter). It happens once a month on the 2nd Tuesday (different this month) and is hosted by a different person in the SQL community each time. The idea is that it’s kind of a rallying point to get a bunch of people to blog about a particular topic on the same day, giving a wide and varied set of opinions and interpretations of that month’s topic. The host then posts a wrap-up commenting on all the contributions. I think it’s a great idea and I contribute whenever I have time.

The host for this month is Paul Randal (Blog | Twitter)  and here is a link to the original invitation for T-SQL Tuesday  post.

In my opinion DBA’s are the bridge between Development and Operations.  DBA’s possess that level of Technical detail that can allow them to speak in SQL but at the same time talk to the end user/PM/Manager/Customer.  A DBA that has these skills can be very effective in fixing problems when they arise.  Many people joke about what DBA stands for, DBA = Default Blame Acceptor typically.  Whether you accept the blame or not as a DBA it’s a fact that typically you will have many fingers pointed at you when something goes wrong.  Typically in the DBA world you are guilty until you prove otherwise. To be able to handle situations that arise regardless of where the blame lands is why you need DBA skills.

DBA’s typically possess 2 very important skills that set them apart.  Being able to see the 30,000 foot view, like it or not the DB is usually the central source for many applications and processes in a company.  The DBA has to understand this and know how lots of different pieces  work together.  They never have the luxury of only writing there one small piece of code that fetches bacon all day long (apGetBacon stored proc would be nice) .  They need to understand the server, network and code to know how it all works together.

DBA’s are usually very patient as well, having the finger pointed at you constantly for performance problems or size issues (I’m speaking of hard drives of course) makes you learn to be patient and work through the problems.  Most of the time it does appear to be a database issue since that is typically what is central to all the different applications in the company so the DBA has to take the time to find the real problem and to defend the database.

It’s a simple fact that the DB is one of the most critical components of many organizations. This fact alone tells us that DBA skills are very necessary to help improve move the business into the future.  While this is a great question to ask I hope that businesses start focus on  when do we need a DBA to handle one of our most precious commodities?

Reads and Writes per DB, Using DMV’s

So years ago when I was working with a SQL 2000 database I had a need to see how many reads and writes were happening on each DB so I could properly partition a new SAN we had purchased. The SAN guys wanted Reads/Sec and Writes/Sec and IO’s/Sec total. Perfmon couldn’t give this for each DB so I had to use fn_virtualFileStats. I wrote a procedure that would tell me per DB what was going on and then store it down into a table for later comparison.

I’ve found a need for this again since I’m running some load tests and want to know what my data files are doing. This is easier now thanks to sys.dm_io_virtual_file_stats. It’s even better now that so many people in the community provide great content! Glen Alan Berry (Blog | Twitter) wrote and excellent DMV a day blog post series and in one of them he gives a great query on Virtual File stats. This gives you an excellent general point in time look at your server but was not exactly what I needed. I wanted to know for a specific period what were my reads and writes. This works better for my load testing needs to know just what is going on during a specific time.

You might want to use this during heavy business hours as well. The DMV is keeping track since the last Server restart so if you look at just the DMV you’re going to see everything that has occurred. Maintenance items (checkdb, Indexes, Backups) will all show up inside there so one DB might be very large in size and at night when the backup kicks off it might be using lots of Reads making it’s percent much higher but during the day no one really uses the DB so the DMV might show you that the DB is very busy when in reality your other DB’s are the busy one’s during the day. So If I’m planning for a new SAN or moving around files I would run this query at specific times so I could compare data points and find out what my databases are actually doing during critical times.

This script takes a Baseline record on the DMV. It then waits the amount of time you specify and takes a comparison line. It then compares the two and returns the percent’s. Lots more could be done with the comparison and certain things I’ve left in for later changes like Size. Right now I don’t do anything with Size but I plan to show the growth from the data points. I chose not to create the script as a stored proc just so it’s easy for you to put where you want. It only deals with 2 data points to keep it simple for now I have considered changing this in the future. The only setting you need to change is the @DelaySeconds parameter. Just set that to the number of seconds you want it to wait. 60 seconds is usually a good default to get a quick snapshot on the server. My suggestion to discover what your databases are doing during busy times I would probably run it for about 300 seconds (5 minutes) and then do that 2-3 times in an hour to see what the data looks like.

Would love to hear any comments on if this works for you!  Thanks.

/*********************************************************************************************
File Stats Per DB
Date Created: 07-22-2010
Written by Pat Wright(@SqlAsylum)
Email: SqlAsylum@gmail.com
Blog: http://Www.Sqlasylum.com
This Scrpit is Free to download for Personal,Educational, and Internal Corporate Purposes,
provided that this main header is kept along with the script.  Sale of this script is
Prohibited in whole or in part is prohibited without the author’s consent.
*********************************************************************************************/

CREATE TABLE #FileStatsPerDb
(
ID INT IDENTITY(1,1) NOT NULL PRIMARY KEY,
[databaseName] [NVARCHAR](128) NULL,
[FileType] [NVARCHAR](60) NULL,
[physical_name] [NVARCHAR](260) NOT NULL,
[DriveLetter] VARCHAR(5) NULL,
[READS] [BIGINT] NOT NULL,
[BytesRead] [BIGINT] NOT NULL,
[Writes] [BIGINT] NOT NULL,
[BytesWritten] [BIGINT] NOT NULL,
[SIZE] [BIGINT] NOT NULL,
[InsertDate] [DATETIME] NOT NULL DEFAULT GETDATE()
)
ON [PRIMARY]

DECLARE @Counter TINYINT
DECLARE @DelaySeconds INT
DECLARE
@TestTime DATETIME

–Set Parameters
/*
The counter is just to initialize the number to 1
The Delayseconds Tells SQL Server how long to wait before it runs the second data point.
How long you want this depends on what your needs are.  If I have a load test running for
5 minutes and I want to know what the read and Write percents were during those 5 minutes
I set it to 300. If I just want a quick look at the system I’ll usually set it to 60 seconds,
To give me a one minute view.  This depends on if it’s a busy time and what’s going on during that time.
*/
SET @Counter = 1
SET @DelaySeconds = 60
SET @TestTime = DATEADD(SS,@delayseconds,GETDATE())

WHILE @Counter <=2
BEGIN
INSERT INTO
#FileStatsPerDb (DatabaseName,FileType,Physical_Name,DriveLetter,READS,BytesRead,Writes,BytesWritten,SIZE)
SELECT
DB_NAME(mf.database_id) AS DatabaseName
,Mf.Type_desc AS FileType
,Mf.Physical_name AS Physical_Name
,LEFT(Mf.Physical_name,1) AS Driveletter
,num_of_reads AS READS
,num_of_bytes_read AS BytesRead
,num_of_writes AS Writes
,num_of_bytes_written AS BytesWritten
,size_on_disk_bytes AS SIZE
FROM sys.dm_io_virtual_file_stats(NULL, NULL) AS fs
JOIN sys.master_files AS mf ON mf.database_id = fs.database_id
AND mf.FILE_ID = fs.FILE_ID
IF @Counter = 1
BEGIN
WAITFOR
TIME @TestTime
END
SET
@Counter = @Counter + 1
END

;
WITH FileStatCTE (Databasename,Filetype,Driveletter,TotalReads,TotalWrites,TotalSize,TotalBytesRead,TotalBytesWritten)
AS
(SELECT BL.Databasename,BL.FileType,Bl.DriveLetter,
NULLIF(SUM(cp.Readsbl.Reads),0) AS TotalReads,
NULLIF(SUM(cp.Writesbl.Writes),0) AS TotalWrites,
NULLIF(((SUM(cp.Sizebl.Size))/1024),0) AS TotalSize,
NULLIF(((SUM(cp.BytesReadbl.BytesRead))/1024),0) AS TotalKiloBytesRead,
NULLIF(((SUM(cp.BytesWrittenbl.BytesWritten))/1024),0) AS TotalKiloBytesWritten
FROM
( SELECT insertdate,Databasename,FileType,DriveLetter,READS,BytesRead,Writes,BytesWritten,SIZE
FROM #FileStatsPerDb
WHERE InsertDate IN (SELECT MIN(InsertDate) FROM #FileStatsPerDb) ) AS BL –Baseline
JOIN
( SELECT insertdate,Databasename,FileType,DriveLetter,READS,BytesRead,Writes,BytesWritten,SIZE
FROM #FileStatsPerDb
WHERE InsertDate IN (SELECT MAX(InsertDate) FROM #FileStatsPerDb) ) AS CP — Comparison
ON BL.Databasename = cp.Databasename
AND bl.filetype = cp.filetype
AND bl.DriveLetter = cp.DriveLetter
GROUP BY BL.databasename,BL.filetype,Bl.driveletter)

/*
Return the Read and write percent for Each DB and file.  Order by ReadPercent
*/
SELECT databasename,filetype,driveletter,
100. * TotalReads / SUM(TotalReads) OVER() AS ReadPercent,
100. * TotalWrites / SUM(TotalWrites) OVER() AS WritePercent
FROM FileStatCTE
ORDER BY ReadPercent DESC,WritePercent DESC

In my haste I forgot to add a sample of what you would get from this.  The names of the DB’s have been changed.

readpercentsample