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Re: log_buffer value does not match spfile value

From: Ron Rogers <>
Date: Thu, 08 Jun 2006 14:04:55 -0400
Message-Id: <>

 Do you have 10g Automatic Memory Management (AMM) turned on? If so then a lot of the init parameters are ignored. To use AMM you set the sga_max_size, sga_target, and pga_aggregate_target parameters in the init. The db_cache_size,db_xk_cache_size, db_keep_cache_size, db_recycle_cache_size, large_pool_size, log_buffer, shared_pool_size, java_pool_size, streams_pool_size, sort_area_size, and hash_area_size become zero, default, or minimum allowing the AMM to increase the size as needed.


>>> "Hallas, John, Tech Dev" <> 06/07/06
10:05 AM >>>  

I have a number of 10G databases where the value of log_buffer in the spfile is not the same as the value within the instance.  

Oracle is obviously deciding it's own value. This is the same on systems
using ASSM and not (sga_target)  

The documentation does not seem to support this but I am sure from a number of instances that this is happening.  

Any ideas on this. Nothing much coming from Metalink. I believe that this is also happening on a databases using an init.ora file rather than
an spfile  



SQL> show parameter log_buffer  

NAME                                 TYPE        VALUE

------------------------------------ -----------

log_buffer                           integer     2097152

SQL> show parameter spfile  

NAME                                 TYPE        VALUE

------------------------------------ -----------

spfile                               string

SQL> !strings /WELDBPROD/u01/oradata/GMSDB/spfileGMSDB.ora | grep -i log_buffer


SQL> show parameter sga_target  

NAME                                 TYPE        VALUE

------------------------------------ -----------

sga_target                           big integer 512M

SQL> show sga  

Total System Global Area 536870912 bytes

Fixed Size                  2030296 bytes

Variable Size             234882344 bytes

Database Buffers          297795584 bytes

Redo Buffers                2162688 bytes

SQL> show parameter shared_pool  

NAME                                 TYPE        VALUE

------------------------------------ -----------

shared_pool_reserved_size            big integer 11324620

shared_pool_size                     big integer 0


Manual SGA parameters are specified by the user, and the given sizes precisely control the sizes of their corresponding components.

When SGA_TARGET is set, the total size of manual SGA size parameters is
subtracted from the SGA_TARGET value, and balance is given to the auto-tuned SGA components.

For example, if SGA_TARGET = 8G and DB_KEEP_CACHE_SIZE = 1G, this means
that the total size of the four auto-tuned components (shared pool, java
pool, default buffer cache, and large pool) is limited to 7GB. The 7GB includes the fixed SGA and log buffer, and only after those have been allocated the rest of the memory is divided between the components. The
size of the keep cache is 1GB, as specified by the parameter.  

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Received on Thu Jun 08 2006 - 13:04:55 CDT

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