Interaction with Operating-System Resource Control

Table 9–7 Modified Priority Plan

The modified plan in Table 9–7 ensures that while the High Priority group gets most of the CPU time, other groups are not completely stalled.

Interaction with Operating-System Resource Control

Oracle9i expects a static configuration and allocates internal resources, such as latches, from available resources detected at database startup. The database might not perform optimally and can become unstable if resource configuration changes very frequently. Therefore, operating-system resource control should be used with Oracle databases judiciously, according to the following guidelines:

1.Operating-system resource control should not be used concurrently with the Database Resource Manager, because neither of them are aware of each other's existence. As a result, both the operating system and Database Resource Manager try to control resource allocation in a manner that causes unpredictable behavior and instability of Oracle databases.

If you want to control resource distribution within an instance, use the Database Resource Manager and turn off operating-system resource control.

If you have multiple instances on a node and you want to distribute resources among them, use operating-system resource control, not the Database Resource Manager.

Note: Oracle9i does not support the use of both tools simultaneously. Future releases might allow for their interaction on a limited scale.

2.In an Oracle environment, the use of an operating-system resource manager, such as Hewlett Packard's Process Resource Manager (PRM) or Sun's Solaris Resource Manager (SRM), is supported only if all of the following conditions are met:

Database Resource Management 9-17

Interaction with Operating-System Resource Control

Each instance must be assigned to a dedicated operating-system resource manager group or managed entity.

The dedicated entity running all the instance's processes must run at one priority (or resource consumption) level.

Process priority management must not be enabled.

Caution: Please note that management of individual Oracle processes at different priority levels (for example, using the nice statement on UNIX platforms) is not supported. Severe consequences, including instance crashes, can result. You can expect similar undesirable results if operating-system resource control is permitted to manage memory on which an Oracle instance is pinned.

3.If you chose to use operating-system resource control, make sure you turn off the Database Resource Manager. By default, the Database Resource Manager is turned off. If it is not, you can turn it off by issuing the following statement:

ALTER SYSTEM SET RESOURCE_MANAGER_PLAN='';

Also remember to reset this parameter in your initialization parameter file, so that the Database Resource Manager is not activated the next time the database is started up.

Dynamic Reconfiguration

Tools such as Sun's processor sets and dynamic system domains work well with an Oracle database. There is no need to restart an instance if the number of CPUs changes.

Oracle dynamically detects any change in the number of available CPUs and reallocates internal resources. On most platforms, Oracle automatically adjusts the value of CPU_COUNT to the number of available CPUs.

See Also: Oracle9i Database Reference for more information on

CPU_COUNT

9-18 Oracle9i Database Concepts