ORACLE_AFFINITY

Enables the scheduling of class threads on more than one processor group for systems with more than 64 CPUs.

This parameter must be manually added. Oracle recommends consulting Oracle Support Services before changing this parameter. The format is:

namen:[[processorgroup0][processorgroup1][..2][..3],]{cpumask0[ cpumask1 cpumask2 cpumask3] | ALL};
name1:[[0][1][2][3],]{cpumask0[ cpumask1 cpumask2 cpumask3] | ALL};
name2:[[0][1][2][3],]{cpumask0[ cpumask1 cpumask2 cpumask3] | ALL};

Where, processorgroup is an optional parameter designating Windows CPU group. On systems with 64+ logical CPUs, Windows divides all available CPUs into 4 groups (0,1,2,3) with each group containing no more than 64 logical CPUs. By default, a process utilizes single processor group. The processorgroup parameter enables Oracle to use more than 64 logical CPUs. Refer to the specific hardware configuration to determine the valid processor groups.

Note:

You should not use the ORACLE_AFFINITY parameter with multiple processor groups on a system with fewer than 64 logical cores. On production servers any system with fewer than 64 logical CPUs can have only one processor group.

Each namen setting must be the name of a background thread, USER for non-background (shadow) threads, or DEF for any thread type not handled specifically. Valid background thread names include DBW0, LGWR, PMON, SMON, ARCH, RECO, CKPT, TRWR, J000 through J999, P000 through P481, and any other name found in the NAME column of the v$bgprocess data dictionary view.

The cpumask sets the affinity mask of the Oracle Database process. Each affinity setting must be a valid affinity mask or its numeric equivalent for the corresponding thread name. Process affinity masks are used only when Oracle Services are first started. Each thread's affinity is set only when the individual thread is started (for example, at database startup time for the background threads).

Few examples, to use multiple processor groups in a system with 160 logical CPUs, ORACLE_AFFINITY registry key in HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\KEY_HOMENAME may be defined as follows:

The following examples show how set the ORACLE_AFFINITY registry key in HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\KEY_HOMENAME to use multiple processor groups in a system with 160 logical CPUs. In the following examples, it is assumed that: USER, DEF are thread class names; 0,1,2,3 are valid CPU groups in the system; and 4294967295 is a valid affinity mask in the corresponding CPU group.

Affinitize USER (foreground) threads to all CPUs in processorgroup1 or to all CPUs in processorgroup2 or to all CPUs in processorgroup3 while alternating between the processor groups for each new foreground thread. Also, affinitize DEF class threads to CPUs 0-31 in processorgroup0.
```
USER:123,ALL;DEF:0,4294967295;
```
Affinitize USER class threads either to CPUs 0-19 in processorgroup0 or to CPUs 16-31 in processorgroup2. Also, affinitize DEF class threads to CPUs 0-19 in processorgroup1.
```
USER:02,1048575 4294901760;DEF:1,1048575;
```
Affinitize USER class threads to all the CPUs of all processor groups while alternating between the processor groups for each new foreground thread. Also, affinitize DEF class threads to CPUs 0-31 in all the processor groups while alternating between the processor groups for each new DEF class thread.
```
USER:0123,ALL;DEF:0123,4294967295;
```
Affinitize USER class threads to CPUs 0-31 in processorgroup0, CPUs 0-19 in processorgroup1 and CPUs 0-19 in processorgroup2 while alternating between the processor groups for each new foreground thread.
```
USER:012,4294967295 1048575 1048575;
```

Parent topic: About HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\KEY_HOMENAME