CPU_COUNT

According to Oracle’s own documentation for 10g release 1:

 

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.

 

The following test was done on an Oracle 9 database running on Tru64:

 

Tru64 > psrinfo -n

number of processors on system = 1

Tru64 > psrinfo -v

Status of processor 0 as of: 12/02/11 15:19:04

  Processor has been on-line since 02/19/2011 17:29:11

  The alpha EV6.7 (21264A) processor operates at 618 MHz,

  has a cache size of 2097152 bytes,

  and has an alpha internal floating point processor.

 

Tru64 > sqlplus '/ as sysdba'

 

SQL*Plus: Release 9.2.0.5.0 - Production on Fri Dec 2 15:19:28 2011

 

Copyright (c) 1982, 2002, Oracle Corporation.  All rights reserved.

 

Connected to:

Oracle9i Enterprise Edition Release 9.2.0.5.0 - Production

With the Partitioning, OLAP and Oracle Data Mining options

JServer Release 9.2.0.5.0 - Production

 

SQL> col value format a10

SQL> col isdefault format a9

SQL> select value, isdefault from v$parameter

  2  where name = 'cpu_count'

  3  /

 

VALUE      ISDEFAULT

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

1          TRUE

 

SQL>

 

The following test was done on an Oracle 9 database running on Linux:

 

Linux > cat /proc/cpuinfo | grep -i 'processor' | wc -l

2

Linux > sqlplus '/ as sysdba'

 

SQL*Plus: Release 9.2.0.4.0 - Production on Fri Dec 2 15:40:12 2011

 

Copyright (c) 1982, 2002, Oracle Corporation.  All rights reserved.

 

Connected to:

Oracle9i Enterprise Edition Release 9.2.0.4.0 - Production

With the Partitioning, OLAP and Oracle Data Mining options

JServer Release 9.2.0.4.0 - Production

 

SQL> col value format a10

SQL> col isdefault format a9

SQL> select value, isdefault from v$parameter

  2  where name = 'cpu_count'

  3  /

 

VALUE      ISDEFAULT

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

2          TRUE

 

SQL>

 

The following test was done on an Oracle 10 database running on Solaris:

 

Solaris > psrinfo -p -v

The physical processor has 2 virtual processors (0 16)

  UltraSPARC-IV+ (portid 0 impl 0x19 ver 0x22 clock 1500 MHz)

The physical processor has 2 virtual processors (2 18)

  UltraSPARC-IV+ (portid 2 impl 0x19 ver 0x22 clock 1500 MHz)

Solaris > sqlplus / as sysdba

 

SQL*Plus: Release 10.2.0.3.0 - Production on Fri Dec 2 15:52:40 2011

 

Copyright (c) 1982, 2006, Oracle.  All Rights Reserved.

 

Connected to:

Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production

With the Partitioning, OLAP and Data Mining options

 

SQL> col isdefault format a9

SQL> col value format a5

SQL> select value, isdefault from v$parameter

  2  where name = 'cpu_count'

  3  /

 

VALUE ISDEFAULT

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

4     TRUE

 

SQL>

 

So it looks as if it works as intended. I went to an Oracle seminar recently, where they said that cpu_count works differently in 11g release 2. Once I have investigated, I will cover this in a future post.