Numa automatically enabled after upgrade to 10.2.0.4
                                                 Last update (2010-06-09 10:22:01)
                                                                                                                   Date added (2009-04-09 09:55:00)

Summary
On HP-UX Itanium Superdome after the upgrade to 10.2.0.4 Oracle automatically stopped using all the cells and from 5 cells uses only the first cell. That had as a result from the 40 cpus of the server, oracle to uses only the first 8.

The upgrade to Oracle 10.2.0.4 automatically changed the initialization parameters to:
_enable_numa_optimization=TRUE
_db_block_numa=5
You can check this specific hidden parameters with the query
SELECT * FROM (
SELECT a.ksppinm AS parameter,
       a.ksppdesc AS description,
       b.ksppstvl AS session_value,
       c.ksppstvl AS instance_value
FROM   x$ksppi a,
       x$ksppcv b,
       x$ksppsv c
WHERE  a.indx = b.indx
AND    a.indx = c.indx
AND    a.ksppinm LIKE '/_%' ESCAPE '/'
ORDER BY a.ksppinm) 
WHERE parameter IN ('_enable_NUMA_optimization', '_db_block_numa')

PARAMETER                                DESCRIPTION                              SESSION_VALUE  INSTANCE_VALUE
---------------------------------------- ---------------------------------------- -------------- ---
_db_block_numa                           Number of NUMA nodes                     1              1
_enable_NUMA_optimization                Enable NUMA specific optimizations       FALSE          FALSE

Workaround
Change the hidden parameters to the following values and restart the database
alter system set "_enable_NUMA_optimization" = FALSE scope = spfile;
alter system set "_db_block_numa" = 1 scope = spfile;
Related information can be found in Metalink:
Doc ID: 760705.1
Oracle Background Processes (Including Parallel Processes) Using Only First 8 CPUs (Half) on 16-CPU Server

Doc ID: 7171446.8
Bug 7171446 - NUMA enabled by default can cause high CPU / OERI

Other related errors to alert.log
ORA-07445:[$PXNMOVE] and ORA-07445:[$COLD_KKERFP()+1984].

Other links
ORA-00600: [kskreconfignuma2], [kskcpucc]
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