| Sorting [message #262808] |
Tue, 28 August 2007 05:34  |
gajini
Messages: 262
Registered: January 2006
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Senior Member |
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Hi,
Is sorting in PGA done by copying blocks from SGA to PGA?
Can anyone explain how it's happening?
Thanks...
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| Re: Sorting [message #263485 is a reply to message #262808] |
Thu, 30 August 2007 03:05  |
gajini
Messages: 262
Registered: January 2006
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Senior Member |
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Hi,
In Oracle doc,it's given that PGA consists of,
1. Stack space (contains session's variables, arrays, and other information)
2. UGA (session-specific data)
in case of Dedicated Server mode.
But in case of MTS,PGA consists of only Stack space & UGA is moved to shared pool or large pool.
My question is,
1. Why UGA is placed in shared memory in case of MTS?
2. If UGA is placed in shared memory since it is shareable among shared server processes,why not stack space placed in shared memory region because it also contains session-specific info?
Can anyone please explain what is the exact difference between contents of Stack space & UGA that makes onething to be placed in shared memory region & other in PGA itself in MTS mode?
Thanks...
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| Re: Sorting [message #263530 is a reply to message #262808] |
Thu, 30 August 2007 04:35 |
gajini
Messages: 262
Registered: January 2006
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Senior Member |
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Thanks Michel for your explanation,
I didn't understand why stack space is not shared.Can you please explain it with an example?
Thanks a lot...
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| Re: Sorting [message #263533 is a reply to message #263530] |
Thu, 30 August 2007 04:42 |
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Michel Cadot
Messages: 68686
Registered: March 2007
Location: Nanterre, France, http://...
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Senior Member
Account Moderator |
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Stack is not shared because it is used only during calls (piece of code execution). During a call you stay with the same shared server, so it can use its own memory and does not need shared memory for stacks.
Between calls there are no more stack.
For instance, you launch a select, a shared server is allocated for you, when it executes your query it allocates (private) memory for stack, when it completes the query it returns you the result and frees space allocated for stack (and forget you).
Regards
Michel
[Updated on: Thu, 30 August 2007 04:45] Report message to a moderator |
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| Re: Sorting [message #263553 is a reply to message #262808] |
Thu, 30 August 2007 05:59 |
gajini
Messages: 262
Registered: January 2006
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Senior Member |
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Michel,a lot of thanks for your good explanation..
Can you please explain me the answer given by you for my first question little briefly,if possible with an example i.e.,
Is sorting in PGA done by copying blocks from SGA to PGA?
Can anyone explain how it's happening?
Soon,with your help & this forum members help I hope i'll learn Oracle DBA well and i'll also start to give solution for others queries...
Thanks Michel & all members of this forum...
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| Re: Sorting [message #263584 is a reply to message #263553] |
Thu, 30 August 2007 08:01 |
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Michel Cadot
Messages: 68686
Registered: March 2007
Location: Nanterre, France, http://...
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Senior Member
Account Moderator |
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| Quote: | Can you please explain me the answer given by you for my first question little briefly
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| Quote: | First block in a buffer area, then data in sort area.
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Is this not briefly?
Process read a block (buffer) in SGA, put it in buffer in PGA then extract data to sort from this buffer and put it in sort area.
| Quote: | Soon,with your help & this forum members help I hope i'll learn Oracle DBA well and i'll also start to give solution for others queries...
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Please first read Database Concepts.
Regards
Michel
[Updated on: Thu, 30 August 2007 08:02] Report message to a moderator |
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