Convert Resource Classes to Workload Groups

Workload groups provide a mechanism to isolate and contain system resources. Additionally, workload groups allow you to set execution rules for the requests running in them. A query timeout execution rule allows runaway queries to be canceled without user intervention. This article explains how to take an existing resource class and create a workload group with a similar configuration. In addition, an optional query timeout rule is added.


See the Mixing resource class assignments with classifiers section in the Workload Classification concept document for guidance on using workload groups and resource classes at the same time.

Understanding the existing resource class configuration

Workload groups require a parameter called REQUEST_MIN_RESOURCE_GRANT_PERCENT that specifies the percentage of overall system resources allocated per request. Resource allocation is done for resource classes by allocating concurrency slots. To determine the value to specify for REQUEST_MIN_RESOURCE_GRANT_PERCENT, use the sys.dm_workload_management_workload_groups_stats DMV. For example, the below query returns a value that can be used for the REQUEST_MIN_RESOURCE_GRANT_PERCENT parameter to create a workload group similar to staticrc40.

SELECT Request_min_resource_grant_percent = Effective_request_min_resource_grant_percent
  FROM sys.dm_workload_management_workload_groups_stats
  WHERE name = 'staticrc40'


Workload groups operate based on percentage of overall system resources.

Because workload groups operate based on percentage of overall system resources, as you scale up and down, the percentage of resources allocated to static resource classes relative to the overall system resources changes. For example, staticrc40 at DW1000c allocates 19.2% of the overall system resources. At DW2000c, 9.6% are allocated. This model is similar if you wish to scale up for concurrency versus allocating more resources per request.

Create Workload Group

With the known REQUEST_MIN_RESOURCE_GRANT_PERCENT, you can use the CREATE WORKLOAD GROUP syntax to create the workload group. You can optionally specify a MIN_PERCENTAGE_RESOURCE that is greater than zero to isolate resources for the workload group. Also, you can optionally specify CAP_PERCENTAGE_RESOURCE less than 100 to limit the amount of resources the workload group can consume.

Using mediumrc as a basis for an example, the below code sets the MIN_PERCENTAGE_RESOURCE to dedicate 10% of the system resources to wgDataLoads and guarantees one query will be able to run all the times. Additionally, CAP_PERCENTAGE_RESOURCE is set to 40% and limits this workload group to four concurrent requests. By setting the QUERY_EXECUTION_TIMEOUT_SEC parameter to 3600, any query that runs for more than 1 hour will be automatically canceled.


Create the Classifier

Previously, the mapping of queries to resource classes was done with sp_addrolemember. To achieve the same functionality and map requests to workload groups, use the CREATE WORKLOAD CLASSIFIER syntax. Using sp_addrolemember only allowed you to map resources to a request based on a login. A classifier provides additional options besides login, such as: - label - session - time The below example assigns queries from the AdfLogin login that also have the OPTION LABEL set to factloads to the workload group wgDataLoads created above.

( WORKLOAD_GROUP = 'wgDataLoads'
 ,MEMBERNAME = 'AdfLogin'
 ,WLM_LABEL = 'factloads')

Test with a sample query

Below is a sample query and a DMV query to ensure the workload group and classifier are configured correctly.

SELECT SUSER_SNAME() --should be 'AdfLogin'

--change to a valid table AdfLogin has access to
  FROM nation
  OPTION (label='factloads')

SELECT request_id, [label], classifier_name, group_name, command
  FROM sys.dm_pdw_exec_requests
  WHERE [label] = 'factloads'
  ORDER BY submit_time DESC

Next steps