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Part VIII: Performance Tuning and Optimization
Exploring the Fundamentals of the Resource Governor
The Resource Governor relies on resource pools, workload groups, and classifi er functions.
This section covers these concepts. You need to understand them before using the Resource
Governor.Understanding the Resource Pool
A resource pool collects physical resources together so that you can manage them. Under
the covers, a resource pool acts as a virtual instance of SQL Server when accessed by an
application. It has a number of parameters including the minimum and maximum values for
the resource. This may include CPU utilization and memory usage. (File I/O is planned for
a later version of SQL Server — most DBAs currently reduce I/O contention by separating
databases, tables, or indexes onto different physical disks.) SQL Server 2012 can have up to
64 user-defi ned resource pools (64-bit versions only), up from the limit of 18 in the previous
release. In addition, there are two built-in pools:■ (^) Internal: Used solely by the Database Engine. This cannot be reconfi gured by the user.
■ (^) Default: Used by all those workloads that have not been assigned to any specifi c
resource pool.
SQL Server DBAs can also defi ne their custom resource pools. The custom resource pools can
defi ne limits for each resource with minimum and maximum values. The sum of all resource
pool minimum values can’t exceed 100 percent. The maximum values for each resource pool
can range from 0 to 100.
A resource pool cannot always operate at its maximum value. The reason for this in most
cases is that the minimum values of all other resource pools can add up to a value that is
too great to enable any given resource pool to operate at its maximum value. For instance,
there might be fi ve resource pools. If four of the resource pools have minimum values of 10
percent, the fi fth resource pool can’t possibly use more than 60 percent because that is all
that remains with all other pools operating at their minimum. The actual maximum for any
pool is the Effective Maximum Rate, which is equal to the difference between the maximum
value of the said resource pool and the sum of the minimum values of all others.
The internal resource pool has a higher priority than all other pools. For this reason it always has an Effective
Maximum Rate of 100 percent. This happens even if the internal pool violates the resource requirements of all other
pools.
Table 50-1 shows fi ve resource pools with the minimum and maximum values for each
resource pool. It also shows the Effective Maximum Rate along with the Shared percent-
age. The Shared percentage is the difference between the Effective Maximum Rate and the
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