11.1. An Overview of the Database Resource Manager

The Database Resource Manager (DRM) offers a component-based approach to resource allocation management. By defining distinct, independent components representing the DRM elements, the result is an extremely flexible and easy-to-use system.

There are three main elements that comprise the DRM:

• Resource consumer groups

• Resource plans

• Resource plan directives

DRM allocates resources among resource consumer groups based on a resource plan. A resource plan consists of resource plan directives that specify how resources should be distributed among the groups. Resource consumer groups are categories to which user sessions can be assigned. These groups can then be allocated resources through plan directives.

Plan directives define resource allocation rules by assigning resource allocation methods to specific resource consumer groups. They connect resource plans to consumer groups and define the resource allocation method to be used.

Resource allocation methods are methods that can be used to allocate resources such as CPU usage, number of sessions, idle time, operation execution time, etc. Resource allocation methods are predefined by Oracle, but plan directives determine which ones to apply and the allocation amounts. For example, a plan named NIGHT_PLAN may contain a directive allocating a percentage of CPU to a consumer group named MANAGERS.