Tuesday, May 12, 2009

CPU_COUNT and related info

URL for more info: http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:36798353051561

INIT.ORA prameter for number of CPUs:cpu_count:The number of CPUs available to Oracle (used to calculate other parameter values). Do not change this value.Range of Values: 0 - unlimited.
Default Value : Automatically set by Oracle
from Metalink:
"On most platforms, Oracle automatically sets the value of CPU_COUNT to the number of CPUs available to your Oracle instance. Do not change the value of CPU_COUNT."


Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> show parameter cpu_count

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
cpu_count integer 4
SQL>
===========================================================================
SQL> SELECT name, value, isdefault FROM v$parameter WHERE name = 'cpu_count';

NAME VALUE ISDEFAULT
--------------------------------------------
cpu_count 4 TRUE
=========================================================================================
ANOTHER SIMILAR PARAMETER:_cpu_count:As per metalink, meant for those "exceptional" Operating Systems, where OS does not support a system call so that Oracle can get the number itself.

So normally this value is not required to be set by DBAs. You have to set this when cpu_count is not showing the actual number of CPUs.

Version Parameter Type Modifiable
11.1.0.6 cpu_count INTEGER ALTER SYSTEM (IMMEDIATE)
10.2.0.4 cpu_count INTEGER ALTER SYSTEM (IMMEDIATE)
10.2.0.3 cpu_count INTEGER ALTER SYSTEM (IMMEDIATE)
10.1.0.5 cpu_count INTEGER ALTER SYSTEM (IMMEDIATE)
10.1.0.4 cpu_count INTEGER ALTER SYSTEM (IMMEDIATE)
9.2.0.8 cpu_count INTEGER Static
9.2.0.8 _cpu_count INTEGER ALTER SYSTEM (IMMEDIATE)
9.0.1.4 cpu_count INTEGER Static
9.0.1.4 _cpu_count INTEGER ALTER SYSTEM (IMMEDIATE)
8.1.7.4 cpu_count INTEGER Static

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