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is there any cache memory for previously ran queries in DB2?

 
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PrabakarV

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Joined: 21 Dec 2007
Posts: 88
Location: My Desk

PostPosted: Fri Apr 09, 2010 11:43 am    Post subject: is there any cache memory for previously ran queries in DB2?
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Hi,

I searched for this topic in DB2 thread bu i could not find what i wanted...

Is there any cache memory for DB2? i ran a query in QMF which took around 10 seconds to respond for the first time i hit F2. But i got the resulst in 1 or 2 seconds when i ran it for second and further...

i dont understand why it takes such a long time for first time and less for further.... Please advice if any of my understanding is incorrect...

Thanks
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GuyC

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Joined: 11 Aug 2009
Posts: 1278
Location: Belgium

PostPosted: Fri Apr 09, 2010 4:57 pm    Post subject:
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1) Bufferpools :
- data(rows&indexes) is stored on disks (=I/O = long elapsed)
- Data is read into bufferpools (memory)
- least used data gets flushed from bufferpool

2) Dynamic Statement Cache :
- Dynamic SQL (like QMF) has to be prepared before execution (= longer CPU and thus longer elapsed)
- those prepared statements are kept in the Dynamic Statement Cache (=memory)
- least used statement gets flushed

3) same things apply to Database description, Packages, ....
A lot of stuff is kept somewhere in memory

This is only DB2.
I'm not such a hardware guy but a lot of storage devices now have their own cache.
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PrabakarV

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PostPosted: Wed Apr 21, 2010 4:43 pm    Post subject:
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Thanks for the help icon_smile.gif
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