Diferencias entre log_buffer y redo buffers

Espero que esto te pueda ayudar!
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Oracle Server-Enterprise and Standard Edition Technical Forum
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Thread Status: Active
From: Joel Patterson 29-Apr-03 18:14
Subject: Redo buffers verses log_buffer
RDBMS Version: 9.2.0.3
Operating System and Version: HP-UX 11i
Error Number (if applicable):
Product (i.e. SQL*Loader, Import, etc.):
Product Version:
Redo buffers verses log_buffer
show sga shows:
Redo Buffers 10760192
select name, value from v$parameter where name = 'log_buffer' shows:
log_buffer 10485760
¿What makes the difference?
[email protected]
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From: Joel Patterson 29-Apr-03 18:23
Subject: Re : Redo buffers verses log_buffer
BTW: my e-mail is [email protected]
[email protected]
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From: Mark Bobak 29-Apr-03 19:05
Subject: Re : Redo buffers verses log_buffer
Joel,
This often seen due to byte boundary alignment and guard pages
added to both sides of the buffer, to help protect against memory
corruption.
-Mark
Mark J. Bobak
Oracle DBA
ProQuest Information and Learning
[email protected]
[email protected]
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From: Joel Patterson 29-Apr-03 21:19
Subject: Re : Redo buffers verses log_buffer
Thanks, I'm trying to write some scripts that select from v$parameter, v$sgastat, etc that will deliver numbers that match 'show sga'. Redo buffers did not match log_buffer.
I'd like to be able to if possible.
Also, if you know, I have two definitions of variable size.
One is variable_size = sga_max_size - fixed_size - database_buffers - redo_buffers. This works when using figures from 'show sga'.
'
'
The other is variable_size = java pool + large pool + shared pool...
so, from v$parameter, I selected java_pool_size, large_pool_size, and shared_pool_size. But this does not work, not even close.
[email protected]
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From: Mark Bobak 29-Apr-03 21:41
Subject: Re : Redo buffers verses log_buffer
Right, that's because variable size is more than shared pool + large
pool + java pool. Those three are the bulk of it, but it can be
affected by number of controlfiles, db_files, transactions, and
many other parameters.
See:
http://asktom.oracle.com/pls/ask/f?p=4950:8:107926810376826036::NO::F4950_P8_DISPLAYID,F4950_P8_CRITERIA:365088445659,
for more info.
-Mark
Mark J. Bobak
Oracle DBA
ProQuest Information and Learning
[email protected]
[email protected]
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From: Joel Patterson 29-Apr-03 22:28
Subject: Re : Redo buffers verses log_buffer
Excelent arcticle:
At the risk of beating a dead horse. The article did bring up more questions. Now I've discovered that: (large_pool_size = 0).
From v$sgastat - sum of bytes on pool
1)
java + shared + large
33554432+201326592+0 = 234881024
but show sga say variable_size = 285212672, a difference of 50331648.
2)
v$sgastat log_buffer = 10749952
show parameter log_buffer = 10485760
show sga Redo buffers = 10760192
(Redo buffers added 5k on either side of sgastat log_buffer I figure as per your explanation.
I'm trying to write a script that will 'show sga', Then compute these figures two ways, and they all should match.
One is variable=sga_max_size-fixed_size-(db_cache_size or db_block_size)- (log_buffer or formula).
The other is to add figures together such as above... variable_size = java + shared + large + something
'
I would not onl