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Oracle® Database Administrator's Guide
11g Release 2 (11.2)

Part Number E17120-11
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Configuring Resource Allocations for Automated Maintenance Tasks

This section contains the following topics on resource allocation for maintenance windows:

About Resource Allocations for Automated Maintenance Tasks

By default, all predefined maintenance windows use the resource plan DEFAULT_MAINTENANCE_PLAN. Automated maintenance tasks run under its subplan ORA$AUTOTASK_SUB_PLAN. This subplan divides its portion of total resource allocation equally among the maintenance tasks.

DEFAULT_MAINTENANCE_PLAN defines the following resource allocations:

Consumer Group/subplan Level 1 Level 2 Maximum Utilization Limit
ORA$AUTOTASK_SUB_PLAN - 25% 90
ORA$DIAGNOSTICS - 5% 90
OTHER_GROUPS - 70%  
SYS_GROUP 75% -  

In this plan, any sessions in the SYS_GROUP consumer group get priority. (Sessions in this group are sessions created by user accounts SYS and SYSTEM.) Any resource allocation that is unused by sessions in SYS_GROUP is then shared by sessions belonging to the other consumer groups and subplans in the plan. Of that allocation, 25% goes to maintenance tasks, 5% goes to background processes performing diagnostic operations, and 70% goes to user sessions. The maximum utilization limit for ORA$AUTOTASK_SUB_PLAN and ORA$DIAGNOSTICS is 90. Therefore, even if the CPU is idle, this group/plan cannot be allocated more than 90% of the CPU resources.

To reduce or increase resource allocation to the automated maintenance tasks, you make adjustments to DEFAULT_MAINTENANCE_PLAN. See "Changing Resource Allocations for Automated Maintenance Tasks" for more information.

Note that as with any resource plan, the portion of an allocation that is not used by a consumer group or subplan is available for other consumer groups or subplans. Note also that the Database Resource Manager does not begin to limit resource allocations according to resource plans until 100% of CPU is being used.

Note:

Although DEFAULT_MAINTENANCE_PLAN is the default, you can assign any resource plan to any maintenance window. If you do change a maintenance window resource plan, ensure that you include the subplan ORA$AUTOTASK_SUB_PLAN and the consumer group ORA$DIAGNOSTICS in the new plan.

See Also:

Chapter 27, "Managing Resources with Oracle Database Resource Manager" for more information on resource plans.

Changing Resource Allocations for Automated Maintenance Tasks

To change the resource allocation for automated maintenance tasks within a maintenance window, you must change the percentage of resources allocated to the subplan ORA$AUTOTASK_SUB_PLAN in the resource plan for that window. (By default, the resource plan for each predefined maintenance window is DEFAULT_MAINTENANCE_PLAN.) You must also adjust the resource allocation for one or more other subplans or consumer groups in the window's resource plan such that the resource allocation at the top level of the plan adds up to 100%. For information on changing resource allocations, see Chapter 27, "Managing Resources with Oracle Database Resource Manager".