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Re: log_buffer value does not match spfile value

Ron Rogers

2006-06-08


John,
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.

Ron

>>> "Hallas, John, Tech Dev" <John.Hallas@(protected)
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



Thanks



John



SQL> show parameter log_buffer



NAME                      TYPE     VALUE

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

log_buffer                  integer   2097152

SQL> show parameter spfile



NAME                      TYPE     VALUE

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

spfile                     string
/WELDBPROD/u01/oradata/GMSDB/s

                                pfileGMSDB.ora

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

*.log_buffer=32768



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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