| What does latch explain? [message #289952] |
Wed, 26 December 2007 21:12  |
trantuananh24hg
Messages: 744
Registered: January 2007
Location: Ha Noi, Viet Nam
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Senior Member |
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Hi all!
This is a brief of statspack report
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Total ----------------- % of Waits ------------------
Event Waits <1ms <2ms <4ms <8ms <16ms <32ms <=1s >1s
-------------------------- ----- ----- ----- ----- ----- ----- ----- ----- -----
latch free 429 7.0 3.0 8.2 8.9 13.5 22.4 26.3 10.7
latch: In memory undo latc 1 100.0
latch: cache buffers chain 287 32.8 6.3 4.5 13.2 7.0 4.9 31.4
latch: cache buffers lru c 4 100.0
latch: checkpoint queue la 1 100.0
latch: library cache 1806 24.3 15.2 15.0 10.9 8.0 8.5 14.7 3.5
latch: library cache lock 17 11.8 5.9 5.9 5.9 70.6
latch: object queue header 6 16.7 33.3 16.7 33.3
latch: parallel query allo 12 25.0 75.0
latch: redo allocation 3 33.3 33.3 33.3
latch: row cache objects 10 40.0 10.0 20.0 30.0
latch: session allocation 106 89.6 3.8 5.7 .9
latch: shared pool 1458 11.6 6.7 16.5 20.7 15.7 9.2 15.7 3.9
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Please explain this brief of latch. I do not understand much, especially about <1ms ; <2ms ; <3ms ; <4ms ...
OS: Solaris 10
Database: 10.2.0
Thank you!
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| Re: What does latch explain? [message #290018 is a reply to message #289952] |
Thu, 27 December 2007 02:54  |
halfydba
Messages: 20
Registered: November 2007
Location: Australia
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Junior Member |
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Simplest way to remember what each is:- Latch is for memory. Lock is for Data. So you have row locks, but memory latches.
In 10g there is a new mechanism called a mutex, which is similar to a latch but (in simple terms) blocks less than a latch.
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