Database Resource Manager
The previous section described some of the ways that you can end up with poor performance
through a lack of CPU resources. The Database Resource Manager (DRM)
was first introduced in Oracle8i and can help youau tomatically avoid some of these
problems.
DRM works by leveraging consumer groups you??™ve identified and enabling you to
place limits on the amount of computer resources that can be used by that group.
Implementing the DRM ensures that one group or member of a group does not end
up using an excessive amount of any one resource, as well as acting to deliver guaranteed
service levels for different sets of users. You can create DRM hierarchies in
which you specify the amount of resources for groups within groups.
The following DRM features can be combined to protect against poor performance:
Predicting resource utilization
The DRM can leverage the query optimizer cost computations to predict the
amount of resources that a given query will take and the query execution time.
Note that, by default, the query optimizer uses a CPU + I/O cost model since
Oracle Database 10g.
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