SQL SERVER – Reducing Page Contention on TempDB

I have recently received following email.

“We are using TraceFlag 1118 to reduce the tempDB contention on our servers (2000 and 2005). What is your opinion?

We have read lots of material, would you please answer me in single line.”

Wow, this was very interesting question. What intrigued me was the second last where I am asked to answer in a single line. There is something about this strong email, I feel like blogging it here.

I think I can talk over this subject forever – well, there is no clear answer. There are so many caveats about everything.  Again, I must stay honest to the request about answering in single line. I also do not like to answer which is YES/NO. What should I do?

Let me ask this question to community today? What will you answer to this email?

Let me start this by answering it myself in one line and taking one side.

“I enable this trace flag in SQL Server 2000 without hot patch or service pack and not in later versions (2005+) onwards as code is improved”.

What do you do in this case? The best answer will feature in this blog with due credit.

Regarding further read and hint here is Microsoft KB which I think is very helpful.

In quick summary: (Read KB for accuracy)

When any page is allocated first 8 pages are allocated in mixed extended. This trace flag allocates uniform extended at the time, reducing contention. You can enable this trace flag at startup.

Reference: Pinal Dave (http://blog.SQLAuthority.com)

SQL SERVER – SQL Challenge – SQL Puzzle – Query Creating Most TempDB IO Usage

Recently, there have been a lot of interesting concepts in various challenges. My friend Jacob Sebastian is running the SQLQuiz for the entire month, and it has been very popular and going just great. So here I thought I would put something very similar to the quiz bee.

The award here is simple, all valid answers will be published on this blog with due credit to you, plus the credit would link back to your desired profile.

Now the question is: What are the queries which are creating lots of IO operations in TempDB?

You can use any DMV to answer this question. You need to list all the operations which are creating IO operations in TempDB, and those which may grow the size TempDB. Sometimes it is not TempDB but the open transactions with lots of queries that can lead to lots of TempDB IO and size growth. In that case, we want to find those open transactions, too. There are no limits as to how many DMVs you can use or how many suggestions you can give. Just find a reason that grows TempDB and creates lots of IO.

I think this is very interesting and many also want to learn the answer for this great question.

Reference: Pinal Dave (http://blog.SQLAuthority.com)

SQL SERVER – How to Drop Temp Table – Check Existence of Temp Table

I have received following questions numerous times:

“How to check existence of Temp Table in SQL Server Database?”

“How to drop Temp Table from TempDB?”

“When I try to drop Temp Table I get following error. Msg 2714, Level 16, State 6, Line 4
There is already an object named ‘#temp’ in the database.
How can I fix it?”

“Can we have only one Temp Table or we can have multiple Temp Table?”

“I have SP using Temp Table, when it will run simultaneously, will it overwrite data of temp table?”

In fact I have already answer this question earlier in one of my blog post. I have even explained how Temp Table works in TempDB and how they are managed.

Visit my earlier written article for answers to questions listed above.

SQL SERVER – Fix : Error : Msg 2714, Level 16, State 6 – There is already an object named ‘#temp’ in the database

Reference : Pinal Dave (http://blog.SQLAuthority.com)

SQL SERVER – Fix : Error : Msg 2714, Level 16, State 6 – There is already an object named ‘#temp’ in the database

Recently, one of my regular blog readers emailed me with a question concerning the following error:

Msg 2714, Level 16, State 6, Line 4
There is already an object named ‘#temp’ in the database.

This reader has been encountering the above-mentioned error, and he is curious to know the reason behind this. Here’s Rakesh’s email.

Hi Pinal,
I’m a  regular visitor to your blog and I thoroughly enjoy your articles and especially the way you solve your readers’ queries. I work as a junior SQL developer in Austin. Today, when I started to create a TSQL application, I detected an interesting scenario.

It is a common practice for many of us to use the following statements to create a new object.But when I used local temporary table, i.e.

IF EXISTS (
SELECT *
FROM sys.tables
WHERE name='#temp')
DROP TABLE #temp
CREATE TABLE #temp(id INT )

An error was displayed as:  Msg 2714, Level 16, State 6, Line 4
There is already an object named ‘#temp’ in the database.

On running the statement
SELECT *
FROM
sys.tables


I see the object under name column in sys.tables as ,
#temp_______________________________________________________________________________________________________________0000000002E1

As far as I can discern, my SQL Server is writing the above entry instead of #temp. Therefore,  I’m getting the error as table already exists – There is already an object named ‘#temp’ in the database. Can you please explain me why this happens to local temporary table?

Thanks and Sincerely Yours,
Rakesh

Rakesh, your question is noteworthy. Let’s look at the solution first and then we will look into the behavior.

Fix/Workaround/Solution:

In case of Temporary tables, run following T-SQL. Please note do not run this for any physical tables. Additionally, please note to replace #temp with yourtemptable name.

IF EXISTS (
SELECT *
FROM sys.tables
WHERE name LIKE '#temp%')
DROP TABLE #temp
CREATE TABLE #temp(id INT )

However, make sure not to run this for physical tables. Additionally, please note to replace #temp with yourtemptable name.
Local temp tables can be created using hash (#) sign prior to table name. They are visible only in current connection.. When connection is dropped its scope ends as well. It is possible to create and use local temp table with the same name simultaneously in two different connections. In order to allow this behavior SQL Server suffixes name of the local temp table with incremental hex digit, which is reset when SQL Services are restarted. It is because of this reason that when looking into sys table it has to compared using LIKE and ‘%’.

Let me create few temporary tables, and then we will observe how hex numbers are suffixed to local temporary tables.

BEGIN
IF
EXISTS (
SELECT *
FROM sys.tables
WHERE name LIKE '#temp%')
DROP TABLE #temp
CREATE TABLE #temp(id INT )
SELECT name
FROM sys.tables
WHERE name LIKE '%#temp%'
END
GO 10

 

Rakesh and my other readers, I encourage all of you to send me interesting and challenging questions that intrigue you as well as observations that you would like to share. As always, I will try my best to answer all your questions. Also, do send me your valuable opinions regarding this article.

Reference : Pinal Dave (http://blog.SQLAuthority.com)

SQL SERVER – Ideal TempDB FileGrowth Value

Just a day ago, while installing SQL Server on our development machine Jr. DBA asked me what should be kept file growth of the TempDB. I really have not thought about this till moment and I looked at MS site.

I found following answer and I think it is quite interesting.

tempdb file size – FILEGROWTH increment for tempdb

0 to 100 MB – 10 MB

100 to 200 MB – 20 MB

500 or more – 10%

Initially you can not know what will be the final size of your TempDB, but as you continue using server for a while and can detect what is the size of the TempDB. Based on your size of TempDB ideal size of FILEGROWTH can be determined.

Reference : Pinal Dave (http://blog.SQLAuthority.com), MS – TempDB

SQL SERVER – T-SQL Script to Find Details About TempDB

Two days ago I wrote article about SQL SERVER – TempDB Restrictions – Temp Database Restrictions. Since then I have received few emails asking details about TempDB. I use following T-SQL Script to know details about my TempDB. I have found this script from MSDN site. I have mentioned original source link in reference at the end of this article.
SELECT
name AS FileName,
size*1.0/128 AS FileSizeinMB,
CASE max_size
WHEN 0 THEN 'Autogrowth is off.'
WHEN -1 THEN 'Autogrowth is on.'
ELSE 'Log file will grow to a maximum size of 2 TB.'
END AutogrowthStatus,
growth AS 'GrowthValue',
'GrowthIncrement' =
CASE
WHEN growth = 0 THEN 'Size is fixed and will not grow.'
WHEN growth > 0
AND is_percent_growth = 0
THEN 'Growth value is in 8-KB pages.'
ELSE 'Growth value is a percentage.'
END
FROM
tempdb.sys.database_files;
GO

Above script will return following result set.

FileName FileSizeinMB AutogrowthStatus GrowthValue GrowthIncrement
tempdev 8 Autogrowth is on. 10 Growth value is a percentage.
templog 0.5 Autogrowth is on. 10 Growth value is a percentage.

Reference : Pinal Dave (http://blog.SQLAuthority.com), BOL

SQL SERVER – TempDB Restrictions – Temp Database Restrictions

While conducting Interview for my outsourcing project, I asked one question to interviewer that what are the restrictions on TempDB? Candidate was not able to answer the question. I thought it would be good for all my readers to know answer to this question so if you face this question in interview or if you meet me in interview you will be able to answer this question.

  • Adding filegroups.
  • Backing up or restoring the database.
  • Changing collation. The default collation is the server collation.
  • Changing the database owner. tempdb is owned by dbo.
  • Creating a database snapshot.
  • Dropping the database.
  • Dropping the guest user from the database.
  • Participating in database mirroring.
  • Removing the primary filegroup, primary data file, or log file.
  • Renaming the database or primary filegroup.
  • Running DBCC CHECKALLOC.
  • Running DBCC CHECKCATALOG.
  • Setting the database to OFFLINE.
  • Setting the database or primary filegroup to READ_ONLY.

Reference : Pinal Dave (http://blog.SQLAuthority.com), BOL