Administrating the Core Database Engine - Microsoft SQL Server 2008 R2 Administration - page 69

Let's see how these RG components and their relationships work with each other as they
exist in the database engine environment. The functions behind the resource governor will
govern the system resource usage such as CPU and memory into separate resource pools
that represent the physical resources of the server. A pool has two parts; one part does not
overlap with other pools by maintaining a minimum (MIN) resource reservation. The other part
is shared with other pools to support maximum (MAX) possible resource consumption.
A workload group serves as a container for session requests that are similar according to the
classification criteria that are applied to each request. RG predefines two workload groups, the
internal group and the default group. These workload groups can be managed by using DDL
statements, such as CREATE , ALTER , and DROP statements that are transactional. However,
the completion of these statements does not make the changes effective. You must execute
the ALTER RESOURCE GOVERNOR RECONFIGURE statement to apply the changes.
A workload group allows the aggregate monitoring of resource consumption and the
application of a uniform policy to all the requests in the group. A group defines the policies for
its members.
Finally, the classification is based on a set of user-written criteria contained in a function. The
logic within this function will control and enable the Resource Governor to classify sessions
into existing workload groups. The only exception for this functionality is using the Dedicated
Administrative Console (DAC) that shall bypass any allocation of the resource group.
The internal workload group is populated with requests that
are for internal use only. You cannot change the criteria
used for routing these requests and you cannot classify
requests into the internal workload group.
As per the previous recipe the function dbo.SalesApp_PROD_classifier() will apply the
configuration changes, then RG classifier will use the workload groups application_Sales
and application_adhoc returned by the function to send a new request to the appropriate
workload group. The overall context of the classification process will begin with login
authentication. This is done by associating a LOGON trigger execution and using the value
returned by the function to send requests to appropriate workload groups.
The execution of the classifier function and LOGON triggers is exposed in sys.dm_exec_
sessions and sys.dm_exec_requests . Refer to the recipe Implementing Tuning and
Monitoring performance for more information on these DMVs.