Microsoft SQL Server 2008 R2 Unleashed- P156 ppt

Reporting Sessions OLTP Sessions Classification Classifier Function Internal Group Internal Pool Group Default Pool Pool 1 Group 2 Pool 2 Query Optimizer FIGURE 40.1 Overview of the Reso

Reporting

Sessions

OLTP Sessions

Classification (Classifier Function)

Internal

Group

Internal

Pool

Group

Default Pool Pool 1

Group 2

Pool 2

Query Optimizer

FIGURE 40.1 Overview of the Resource Governor

NOTE

Resource Governor is available only in the Enterprise, Datacenter, and Developer

Editions of SQL Server 2008 and SQL Server 2008 R2

Overview of Resource Governor

Resource Governor works by controlling the allocation of resources according to

work-loads When a connection request is submitted to the Database Engine, the request is

clas-sified based on a classification function The classification function is a scalar function

that you define via T-SQL The classification function evaluates information about the

connection (for example, login ID, application name, hostname, server role) to determine

how it should be classified After the connection request is classified, it is routed to a

workload group defined for that classification (or if the connection cannot be classified, it

is routed to the default workload group) Each workload group is associated with a

resource pool A resource pool represents the physical resources of SQL Server (currently in

SQL Server 2008, the only physical resources available for configuration are CPU and

memory) and specifies the maximum amount of CPU and/or memory resources that are to

be allocated to a specific type of workload When a connection is classified and put into

the correct workload group, the connection is allocated the CPU and memory resources

assigned to it, and then the query is passed on to the query optimizer for execution This

process is illustrated in Figure 40.1

Resource Governor is designed to address the following types of resource issues, which are

commonly found in a database environment:

Runaway queries—These resource-intensive queries can take up most or all of the

server resources

Unpredictable workload execution—This situation occurs when you have

concurrent applications on the same server that are not isolated from each other,

and the resulting resource contention causes unpredictable performance

Workload prioritization—You might want to ensure that a critical workload is

given priority to the system resources so it can process faster than other workloads

or is guaranteed to complete if there is resource contention

In addition to enabling you to classify incoming connections and route their workloads to

a specific group, Resource Governor also enables you to do the following:

Monitor resource usage for each workload in a group

Pool resources and set pool-specific limits on CPU usage and memory allocation,

which can prevent or minimize the probability of runaway queries

Associate grouped workloads with a specific pool of resources

Identify and set priorities for workloads

The current release of Resource Governor has the following limitations:

Resource allocation is only for CPU and memory usage There is no support for

managing network and disk I/O resource utilization

Resource Governor manages only resource consumption of the Database Engine You

cannot use Resource Governor to manage workloads within SSAS, SSIS, or SSRS

In the following sections, you learn how to set up and configure Resource Governor for

use, how Resource Governor works under the hood, and how you can use Resource

Governor to better prioritize and manage a SQL Server’s workload

Resource Governor Components

Resource Governor consists of three main components: classification, workload groups,

and resource pools Understanding these three components and how they interact is

important to understanding and using Resource Governor

Classification

Classification is the process of evaluating incoming user connections and assigning them

to a workload group Classification is performed by logic contained in a user-defined

func-tion The function returns the workload group name, which Resource Governor uses to

route the sessions into the appropriate workload groups

When Resource Governor is configured, the login process for a session consists of the

following steps:

1 Login authentication

2 LOGON trigger execution

3 Classification

Workload Groups

Workload groups are the containers for similar connections, which are grouped together as

similar according to the classification criteria applied to each connection A workload

group also provides the mechanism for aggregate monitoring of resource consumption

Resource Governor has two predefined workload groups: the internal group and default

group The internal workload group is used solely by internal Database Engine processes

You cannot change the classification criteria for the internal group, and you also cannot

classify any user requests for assignment to the internal group You can, however, monitor

the internal group

Connection requests are automatically classified into the default group when the

follow-ing conditions exist:

There are no criteria to classify a request

There is an attempt to classify the request into a nonexistent group

There is a general classification failure

Resource governor supports a total of 20 workload groups Because two of them are

reserved for the internal and default workload groups, a total of 18 user-defined workload

groups can be defined

Resource Pools

A resource pool, or pool, represents the allocation of physical resources of the SQL Server A

resource pool has two parts:

The first part specifies the minimum resource reservation This part of the resource

pool does not overlap with other pools

The other part specifies the maximum possible resource reservation for the pool The

resource allocation is shared with other pools

In SQL Server 2008 and SQL Server 2008 R2, the pool resources are set by specifying a MIN

orMAXallocation for CPU and a MINorMAXallocation for memory The MINsetting specifies

the minimum guaranteed resource availability of the pool The MAXsetting sets the

maximum size of the pool for each of the resources

Because there cannot be any overlap in the minimum resource reservation, the sum of the

MINvalues across all pools cannot exceed 100% of the total server resources The ensures

that each pool is guaranteed the specified resource allocation

TheMAXvalue can be set anywhere in the range between the MINvalue and 100%

inclu-sive The MAXsetting represents the maximum amount of resources a session can consume,

as long as the resources are available and not in use by another pool that is configured

with a nonzero MIN value When a pool has a nonzero MINpercentage defined, the

effec-tiveMAXvalue of other pools is readjusted down, as necessary, to the existing MAXvalue

minus the sum total of the MINvalues of other pools

For example, consider you have two user-defined pools One pool, Pool1, is defined with a

MINsetting of 20% and a MAXsetting of 100% The other pool, Pool2, is defined with a MIN

setting of 50% and a MAXsetting of 70% The resulting effective MAX setting for Pool1 is

50% (100% minus the MIN50% of Pool2) The effective MAXsetting of Pool2, however,

remains at 70% rather than 80% because 70% is the configured MAXvalue of Pool2

The shared part of the pool (the amount between the MINand effective MAXvalues) is used

to determine the amount of resources that can be consumed by the pool if the resources

are available and not being consumed by another pool When resources are consumed by

a pool, they are assigned to the specified pool and are not shared until processing

completes in that pool

To illustrate this further, consider a scenario in which there are three user-defined

resource pools:

PoolA is defined with a MIN %of 10 and MAX %of 100

PoolB is defined with a MIN %of 35 and a MAX %of 90

PoolC is defined with a MIN %of 30 and a MAX %of 80

The effective MAXof PoolA would be calculated as follows:

MAX %of PoolA 100

minusMIN %of PoolB 35

minusMIN %of PoolC 30

equalsEFF MAXof PoolA 35

The total Shared %of resources of PoolA would then be calculated as follows:

EffectiveMAX% of PoolA 35

minusMIN %of PoolA 10

equalsShared %of PoolA 25

Table 40.1 illustrates the calculated effective MAXandShared %values for all pools in this

configuration

To coincide with the predefined workload groups, Resource Governor also has two

prede-fined resource pools: the internal pool and default pool

The internal pool represents the resources consumed by the internal processes of the

Database Engine This pool always contains only the internal group, and the pool is not

alterable in any way The Internal Pool has a fixed MIN %of 0 and a MAX %of 100, and

resource consumption by the internal pool is not restricted or reduced by any settings in

other pools In other words, the effective MAXof the Internal Pool is always 100% Any

workloads in the internal pool are considered critical for server function, and Resource

Governor allows the internal pool to consume 100% of available resources if necessary,

even if it means the violation of the resource requirements of the other pools

The default pool is the first predefined user pool Prior to any configuration, the default pool

contains only the default group The default pool cannot be created or dropped, but it can be

altered The default pool can contain user-defined groups in addition to the default group

Now that you have an understanding of the Resource Governor components, let’s put

them into use by enabling and setting up some resource groups

Configuring Resource Governor

To begin using Resource Governor for managing the resources of your workloads, follow

these steps:

1 Enable Resource Governor

2 Create your user-defined resource pools

3 Define your workload groups and assign them to pools

4 Create the classifier function

5 Register the classifier function with the Resource Governor

NOTE

Resource Governor can be set up and managed using either SQL Server Management

Studio (SSMS) or via T-SQL commands In the following sections, we first show you

how to perform the tasks in SSMS and how the same actions can be implemented

using T-SQL

TABLE 40-1 EffectiveMAX and Shared % Values for Multiple Pools

ResourcePool MIN % MAX % EffectiveMAX % Shared %

FIGURE 40.2 Enabling Resource Governor in SSMS

Enabling Resource Governor

Before you can begin creating your resource pools, you need to enable the Resource

Governor first To enable Resource Governor in SSMS, in Object Explorer, expand the

Managementnode, right-click on the Resource Governornode, and select Enable (see

Figure 40.2)

Alternatively, you can also enable Resource Governor by using the ALTER RESOURCE

GOVERNORcommand in T-SQL:

ALTER RESOURCE GOVERNOR RECONFIGURE

When Resource Governor is not enabled, the RECONFIGUREoption enables Resource

Governor Enabling Resource Governor has the following results:

The classifier function, if defined, is executed for new connections so that their

workload can be assigned to workload groups

The resource limits specified in the Resource Governor configuration are honored

and enforced

Any connections that existed before Resource Governor was enabled are now

affect-ed by any configuration changes made when Resource Governor was disablaffect-ed

When Resource Governor is already enabled, the RECONFIGUREoption must be executed to

apply any configuration changes made using the CREATE|ALTER|DROP WORKLOAD GROUPor

CREATE|ALTER|DROP RESOURCE POOLstatements

To determine whether Resource Governor is currently enabled, you can run a SELECT

state-ment against the sys.resource_governor_configurationsystem catalog table to view the

is_enabledcolumn:

select is_enabled from sys.resource_governor_configuration

go

is_enabled

-1

To determine whether anyRESOURCE GOVERNORconfiguration changes are pending, you can

use thesys.dm_resource_governor_configurationdynamic management view (DMV):

select is_reconfiguration_pending

from sys.dm_resource_governor_configuration

go

is_reconfiguration_pending

-0

To disable Resource Governor, right-click on the Resource Governornode and select

Disable or execute the following command in T-SQL:

ALTER RESOURCE GOVERNOR DISABLE

Defining Resource Pools

When setting up a Resource Pool, you have to specify a name for the pool and set its

properties The properties available for a resource pool are

Name—The name used to refer to the resource pool

Minimum CPU %—The guaranteed average CPU bandwidth for all requests to the

resource pool when there is CPU contention

Maximum CPU %—The maximum average CPU bandwidth for all requests to the

resource pool when there is CPU contention

Min Memory %—The guaranteed minimum amount of memory reserved for the

resource pool that cannot be shared with other resource pools

Max Memory %—The total server memory that can be used by requests to the

resource pool

Creating a Resource Pool in SSMS

The following steps walk you through using SSMS to create a resource pool named

ReportPoolthat you’ll configure for handling report query workloads:

FIGURE 40.3 Creating a resource pool in SSMS

1 In Object Explorer, expand the Managementnode for a SQL Server Instance and

expand the Resource Governornode

2 Right-click on Resource Pools and select New Resource Pool to open the Resource

Governor Properties page (see Figure 40.3)

3 In the Resource Pools grid, click the first column in the empty row This row is

labeled with an asterisk (*)

NOTE

If the Resource Pools grid does not have a row labeled with an asterisk, Resource

Governor has not been enabled yet You can enable Resource Governor without leaving

the Resource Governor Properties page by putting a check mark in the Enable

Resource Governor check box

4 Double-click the empty cell in the Namecolumn Type in the name that you want to

use for the resource pool For this example, use the name ReportPool

5 Set the CPU and Memory resource values In this example, leave the Min CPU %and

Min Memory %values at 0 and configure the Max CPU %andMax Memory %values at

20 and 30, respectively

6 To create the pool and exit the dialog, click OK

To verify that the new pool was created, you expand the Resource Poolsfolder under the

Resource Governornode and look for a node named ReportPool Alternatively, you can

run a query against the sys.resource_governor_resource_poolsdynamic management

view, similar to the following, which also displays the resource pool configuration:

select name,

min_cpu_percent as MinCPU,

max_cpu_percent as MaxCPU,

min_memory_percent as ‘MinMEM%’ ,

max_memory_percent as ‘MaxMEM%’

from sys.resource_governor_resource_pools

go

name MinCPU MaxCPU MinMEM% MaxMEM%

- - -

-internal 0 100 0 100

default 0 100 0 100

ReportPool 0 20 0 30

Creating a Resource Pool in T-SQL

Now that you’ve set up the ReportPoolresource pool in SSMS, you are able to set up a

second resource pool, OLTPPool, using T-SQL The command to create a resource pool,

CREATE RESOURCE POOL, takes four arguments: MIN_CPU_PERCENT,MAX_CPU_PERCENT,

MIN_MEMORY_PERCENT, and MAX_MEMORY_PERCENT After creating the resource pool, you need

to run ALTER RESOURCE GOVERNOR RECONFIGUREto apply the new resource pool:

CREATE RESOURCE POOL OLTPPool

WITH

(min_cpu_percent=80,

max_cpu_percent=100,

min_memory_percent=75,

max_memory_percent=100)

GO

ALTER RESOURCE GOVERNOR RECONFIGURE;

GO

Now that you’ve defined the resource pools needed, the next step is to define your

work-load groups and associate them with a resource pool

Defining Workload Groups

After you define your resource pools, the next step is to create the workload groups and

associate them with the appropriate resource pools Multiple workgroups can be assigned

to that same pool, but a workgroup cannot be assigned to multiple resource pools

Creating Workload Groups in SSMS

To create a workload group in SSMS, perform the following steps:

1 In Object Explorer, expand the Managementnode, right-click the Resource Governor

node, and then click Properties to bring up the Resource Governor Properties page

2 In the Resource Pools grid, click the row for the resource pool you want to create a

workload groupfor (in this example, the ReportPoolresource pool) This creates a

new empty row in the Workload Groups for Resource Pool grid for that pool

3 Double-click the empty cell in the Namecolumn for the empty workload group row

and type in the name you want to use for the workload group (for this example,

ReportWG1) and any other properties you want to specify (see Figure 40.4)

4 Click OK to exit the Properties page and create the workload group

The additional, optional properties available for workload groups let you set a finer level

of control over the execution of queries within a workload group The options available

are

Importance—Specifies the relative importance (LOW,MEDIUM, or HIGH) of the

work-load group within the resource pool If you define multiple workwork-load groups in a

FIGURE 40.4 Creating a Workload Group in SSMS