Diferencias entre log_buffer y redo buffers

¿Cuál es la diferencia entre log_buffer y redo buffers?
Si los REDO BUFFERS forman parte del buffer de redo log y LOG_BUFFER es un parametros que define el tamaño de este buffer de redo log, como es que el redo buffer (667648) es mayor que el log_buffer(524288). Por lo visto no entiendo la definición de ambos.
Saludos, Tamara
SQL> startup;
Instancia ORACLE iniciada.
Total System Global Area 135338868 bytes
Fixed Size 453492 bytes
Variable Size 109051904 bytes
Database Buffers 25165824 bytes
Redo Buffers 667648 bytes
Base de datos montada.
Base de datos abierta.
SQL> show parameter log_buffer;
NAME TYPE VALUE
-------------------------------
log_buffer integer 524288
1

1 Respuesta

55.075 pts. Ing. de Sistemas mencion Sumacumlaudem Consultor de...
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

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