Creating a Complex Resource Plan

About the Pending Area

The pending area is a staging area where you can create a new resource plan, update an existing plan, or delete a plan without affecting currently running applications. When you create a pending area, the database initializes it and then copies existing plans into the pending area so that they can be updated.

After you make changes in the pending area, you validate the pending area and then submit it. Upon submission, all pending changes are applied to the data dictionary, and the pending area is cleared and deactivated.

If you attempt to create, update, or delete a plan (or create, update, or delete consumer groups or resource plan directives) without first creating the pending area, you receive an error message.

Submitting the pending area does not activate any new plan that you create; it just stores new or updated plan information in the data dictionary. However, if you modify a plan that is currently active, the plan is reactivated with the new plan definition. See "Enabling Oracle Database Resource Manager and Switching Plans" for information about activating a resource plan.

When you create a pending area, no other users can create one until you submit or clear the pending area or log out.

Creating a Pending Area

You create a pending area with the CREATE_PENDING_AREA procedure.

Example: Creating a pending area:

The following PL/SQL block creates and initializes a pending area:

BEGIN
  DBMS_RESOURCE_MANAGER.CREATE_PENDING_AREA();
END;
/

Creating Resource Consumer Groups

You create a resource consumer group using the CREATE_CONSUMER_GROUP procedure. You can specify the following parameters:

Example: Creating a Resource Consumer Group

The following PL/SQL block creates a consumer group called OLTP with the default (ROUND-ROBIN) method of allocating resources to sessions in the group:

BEGIN
  DBMS_RESOURCE_MANAGER.CREATE_CONSUMER_GROUP (
   CONSUMER_GROUP => 'OLTP',
   COMMENT        => 'OLTP applications');
END;
/

Creating a Resource Plan

You create a resource plan with the CREATE_PLAN procedure. You can specify the parameters shown in the following table. The first two parameters are required. The remainder are optional.

Example: Creating a Resource Plan

The following PL/SQL block creates a resource plan named DAYTIME:

BEGIN
  DBMS_RESOURCE_MANAGER.CREATE_PLAN(
   PLAN    => 'DAYTIME',
   COMMENT => 'More resources for OLTP applications');
END;
/

Creating Resource Plan Directives

You use the CREATE_PLAN_DIRECTIVE procedure to create resource plan directives. Each directive belongs to a plan or subplan and allocates resources to either a consumer group or subplan.

You can specify the following parameters:

Example 1:

The following PL/SQL block creates a resource plan directive for plan DAYTIME. (It assumes that the DAYTIME plan and OLTP consumer group are already created in the pending area.)

BEGIN
  DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE (
   PLAN             => 'DAYTIME',
   GROUP_OR_SUBPLAN => 'OLTP',
   COMMENT          => 'OLTP group',
   MGMT_P1          => 75);
END;
/

This directive assigns 75% of CPU resources to the OLTP consumer group at level 1.

To complete the plan shown in Figure 27-1, you would create the REPORTING consumer group, and then execute the following PL/SQL block:

BEGIN
  DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE (
   PLAN                     => 'DAYTIME', 
   GROUP_OR_SUBPLAN         => 'REPORTING',
   COMMENT                  => 'Reporting group',
   MGMT_P1                  => 15,
   PARALLEL_DEGREE_LIMIT_P1 => 8,
   ACTIVE_SESS_POOL_P1      => 4);

  DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE (
   PLAN                     => 'DAYTIME', 
   GROUP_OR_SUBPLAN         => 'OTHER_GROUPS',
   COMMENT                  => 'This one is required',
   MGMT_P1                  => 10);
END;
/

In this plan, consumer group REPORTING has a maximum degree of parallelism of 8 for any operation, while none of the other consumer groups are limited in their degree of parallelism. In addition, the REPORTING group has a maximum of 4 concurrently active sessions.

Example 2:

This example uses the RATIO method to allocate CPU, which uses ratios instead of percentages. Suppose your application suite offers three service levels to clients: Gold, Silver, and Bronze. You create three consumer groups named GOLD_CG, SILVER_CG, and BRONZE_CG, and you create the following resource plan:

BEGIN
  DBMS_RESOURCE_MANAGER.CREATE_PLAN
   (PLAN             => 'SERVICE_LEVEL_PLAN',
    MGMT_MTH         => 'RATIO', 
    COMMENT          => 'Plan that supports three service levels');

  DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE
   (PLAN             => 'SERVICE_LEVEL_PLAN',
    GROUP_OR_SUBPLAN => 'GOLD_CG', 
    COMMENT          => 'Gold service level customers',
    MGMT_P1          => 10);
  DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE
   (PLAN             => 'SERVICE_LEVEL_PLAN',
    GROUP_OR_SUBPLAN => 'SILVER_CG', 
    COMMENT          => 'Silver service level customers',  
    MGMT_P1          => 5);
  DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE
   (PLAN             => 'SERVICE_LEVEL_PLAN',
    GROUP_OR_SUBPLAN => 'BRONZE_CG', 
    COMMENT          => 'Bronze service level customers',
    MGMT_P1          => 2);
  DBMS_RESOURCE_MANAGER.CREATE_PLAN_DIRECTIVE
    (PLAN            => 'SERVICE_LEVEL_PLAN', 
    GROUP_OR_SUBPLAN => 'OTHER_GROUPS',
    COMMENT          => 'Lowest priority sessions',
    MGMT_P1          => 1);
END;
/

The ratio of CPU allocation is 10:5:2:1 for the GOLD_CG, SILVER_CG, BRONZE_CG, and OTHER_GROUPS consumer groups, respectively.

If sessions exist only in the GOLD_CG and SILVER_CG consumer groups, then the ratio of CPU allocation is 10:5 between the two groups.

Validating the Pending Area

At any time when you are making changes in the pending area, you can call VALIDATE_PENDING_AREA to ensure that the pending area is valid so far.

The following rules must be adhered to, and are checked by the validate procedure:

• No plan can contain any loops. A loop occurs when a subplan contains a directive that references a plan that is above the subplan in the plan hierarchy. For example, a subplan cannot reference the top plan.

• All plans and resource consumer groups referred to by plan directives must exist.

• All plans must have plan directives that point to either plans or resource consumer groups.

• All percentages in any given level must not add up to greater than 100.

• A plan that is currently being used as a top plan by an active instance cannot be deleted.

• The following parameters can appear only in plan directives that refer to resource consumer groups, not other resource plans:

  • PARALLEL_DEGREE_LIMIT_P1

  • ACTIVE_SESS_POOL_P1

  • QUEUEING_P1

  • SWITCH_GROUP

  • SWITCH_TIME

  • SWITCH_ESTIMATE

  • SWITCH_IO_REQS

  • SWITCH_IO_MEGABYTES

  • MAX_EST_EXEC_TIME

  • UNDO_POOL

  • MAX_IDLE_TIME

  • MAX_IDLE_BLOCKER_TIME

  • SWITCH_FOR_CALL

  • MAX_UTILIZATION_LIMIT

• There can be no more than 28 resource consumer groups in any active plan. Also, at most, a plan can have 28 children.

• Plans and resource consumer groups cannot have the same name.

• There must be a plan directive for OTHER_GROUPS somewhere in any active plan. This ensures that a session that is not part of any of the consumer groups included in the currently active plan is allocated resources (as specified by the directive for OTHER_GROUPS).

VALIDATE_PENDING_AREA raises an error if any of the preceding rules are violated. You can then make changes to fix any problems and call the procedure again.

It is possible to create "orphan" consumer groups that have no plan directives referring to them. This allows the creation of consumer groups that will not currently be used, but might be part of some plan to be implemented in the future.

Example: Validating the Pending Area:

The following PL/SQL block validates the pending area.

BEGIN
  DBMS_RESOURCE_MANAGER.VALIDATE_PENDING_AREA();
END;
/

Submitting the Pending Area

After you have validated your changes, call the SUBMIT_PENDING_AREA procedure to make your changes active.

The submit procedure also performs validation, so you do not necessarily need to make separate calls to the validate procedure. However, if you are making major changes to plans, debugging problems is often easier if you incrementally validate your changes. No changes are submitted (made active) until validation is successful on all of the changes in the pending area.

The SUBMIT_PENDING_AREA procedure clears (deactivates) the pending area after successfully validating and committing the changes.

Example: Submitting the Pending Area:

The following PL/SQL block submits the pending area:

BEGIN
  DBMS_RESOURCE_MANAGER.SUBMIT_PENDING_AREA();
END;
/

Clearing the Pending Area

There is also a procedure for clearing the pending area at any time. This PL/SQL block causes all of your changes to be cleared from the pending area and deactivates the pending area:

BEGIN
  DBMS_RESOURCE_MANAGER.CLEAR_PENDING_AREA();
END;
/

After calling CLEAR_PENDING_AREA, you must call the CREATE_PENDING_AREA procedure before you can again attempt to make changes.