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Tempdb issue Expand / Collapse
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Posted Friday, July 19, 2013 10:15 AM
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Steve-3_5_7_9 (7/10/2013)
kevaburg (7/9/2013)
There is nothing to worry about. TempDB is recreated each time the instance/server is restarted and it will consume however much space it requires to perform its function. The fact it is so small by a restart is nothing to be concerned about as (by the very nature of the file itself) the data contained within is temporary.



It absolutely is something to be concerned about. You want to have TempDB properly sized, so in this case the OP would want to size it at 2GB or higher. If you allow TempDB to "autogrow" you will most likely have performance issues as the TempDB file(s) grow.

Steve


This is something that could become very contentious. Why would growth on the TEMPDB be a problem if the database itself is properly sized (the DB determines that itself) and growth rate is properly set?

This, from my point of view, only becomes a problem if the database server is restarted on a regular basis. The people that insist on restarting a Windows Server / Database Server make this a problem all by themselves.

I don't think the problem is in answering the question "why doesn't it maintain the settings I give it" rather "why was the instance restarted in the first place?"

Because TEMPDB is recreated each time the instance is started, it must also be populated each time the instance starts with the data the needs to be loaded. Resizing (if done properly) is not a huge issue in SQL Server although I am not taking away the fact that it requires resources to perform. The most intensive operation here is repopulating the database so it can operate in the way it should. This is the equivalent of restarting an Oracle database and wondering why each initial query execution is slower than normal simply because the shared pool has been flushed.

Anyway, that is why I believe it isn't a problem.....

(Sorry the answer took so long.....hoilday has a somewhat higher priority!)
Post #1475579
Posted Friday, July 19, 2013 10:57 AM
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I'm not sure I completely understand your reply, but it seems as though your saying just let TempDB grow as needed.

TempDB should be sized just like any other database. One should know their workload, or at least monitor the TempDB over several weeks to see what is a healthy size for it. Once this is determined, you then can set the size of the TempDB, so that when the server is restarted, it will be at the correct size, thereby having to use "auto grow".

"auto grow" on TempDB and other database can cause serious performance issues, and only be used as a safety net.

As far as "repopulating" TempDB being important. What would it be repopulated with? This database only exists for temporary operations. Once a connection is closed any "temp" objects created (tables, views, etc..) by that SPID will be dropped. TempDB doesn't store query cache, execution plans, or stats. A restart of the server flushes the cache, memory.

Steve



Post #1475606
Posted Friday, July 19, 2013 11:25 AM


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Steve-3_5_7_9 (7/19/2013)


TempDB should be sized just like any other database. One should know their workload, or at least monitor the TempDB over several weeks to see what is a healthy size for it. Once this is determined, you then can set the size of the TempDB, so that when the server is restarted, it will be at the correct size, thereby having to use "auto grow".



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Post #1475610
Posted Friday, July 19, 2013 7:28 PM


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kevaburg (7/19/2013)
Steve-3_5_7_9 (7/10/2013)
kevaburg (7/9/2013)
There is nothing to worry about. TempDB is recreated each time the instance/server is restarted and it will consume however much space it requires to perform its function. The fact it is so small by a restart is nothing to be concerned about as (by the very nature of the file itself) the data contained within is temporary.



It absolutely is something to be concerned about. You want to have TempDB properly sized, so in this case the OP would want to size it at 2GB or higher. If you allow TempDB to "autogrow" you will most likely have performance issues as the TempDB file(s) grow.

Steve


This is something that could become very contentious. Why would growth on the TEMPDB be a problem if the database itself is properly sized (the DB determines that itself) and growth rate is properly set?

This, from my point of view, only becomes a problem if the database server is restarted on a regular basis. The people that insist on restarting a Windows Server / Database Server make this a problem all by themselves.

I don't think the problem is in answering the question "why doesn't it maintain the settings I give it" rather "why was the instance restarted in the first place?"

Because TEMPDB is recreated each time the instance is started, it must also be populated each time the instance starts with the data the needs to be loaded. Resizing (if done properly) is not a huge issue in SQL Server although I am not taking away the fact that it requires resources to perform. The most intensive operation here is repopulating the database so it can operate in the way it should. This is the equivalent of restarting an Oracle database and wondering why each initial query execution is slower than normal simply because the shared pool has been flushed.

Anyway, that is why I believe it isn't a problem.....

(Sorry the answer took so long.....hoilday has a somewhat higher priority!)


I guess I don't understand what you're talking about when you speak of "repopulating" TempDB. TempDB requires no repopulation on restart. Some things in the system do use it once TempDB has been restarted but it doesn't require "repopulation" in any classic sense. Allocating the space for it takes no time if you have instant allocation enabled. And, TempDB has nothing to do with "shared pool" stuff. That would memory/cache where data and execution plans are loaded and, hopefully, reused. TempDB has little to do with any of that.

Perhaps when you're speaking of "repopulating 'the DB'", you're not talking about TempDB but are talking about some other data DB?


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Post #1475721
Posted Sunday, July 21, 2013 7:51 AM


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Hi,

There are some existing recommendations for the tempdb files. These two are most advised:
- If the server has more than 8 cores then start with 8 tempdb files; or
- The number of tempdb files should be 1/4 to 1/2 of the number of cores.

For the "proportional fill" algorithm it's vital the sizes and growths be equal for all files.

Regards,
IgorMi




Igor Micev,
SQL Server developer at Seavus
www.seavus.com
Post #1475820
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