The Real MTCS SQL Server 2008 Exam 70/432 Prep Kit- P124 pptx

PerformanceTuning•Chapter13 597 customers, realizing many benefits of better hardware utilization and more cost- effective database deployments. However consolidation does have some drawbacks. The most common objections to server consolidation is performance, because shared (multi-instance) servers and shared SQL Server instances can introduce challenges in ensuring consistent performance for all database users. Common problems arise from mixed users where regular OnLine Transaction Processing (OLTP) users mix with reporting users on the same instance; examples can be found where databases for the finance department combine with sales order databases. In this situation, normal database traffic consisting of inserts, updates, and deletes can conflict with the work- load generated by reports run by finance users executing month- or year-end reports based on historic sales data. The Resource Governor was introduced to SQL Server 2008 to provide predictable performance for mission-critical workloads. Resource Governor achieves predictable performance by monitoring and reserving minimum levels of critical resources such as CPU and memory for specific tasks or groups of tasks. Resource Governor Concepts The Resource Governor consists of three key concepts: Resource Pools, Workload Groups, and Classification Functions. The Resource Governor exists to manage minimum resources available for different groups of users or tasks. However the governor is more intelligent than simply dividing resources among users; if resources are unused elsewhere on a server, a given user can be permitted to use excess of their quota (up to a maximum allocation) until a time when another user or process requires the resource (memory or CPU). This section introduces each concept and uses an example to illustrate the purpose and implementation of the concept. The example relates to a college whereby requests from lecturers should receive priority over requests received from students. Resource Pools Resource pools are used to manage minimum and maximum restrictions on physical server resources. Conceptually, Resource Pools enable multiple virtual SQL Server instances to operate within a single physical instance. Each pool (virtual instance) is allocated a minimum and maximum CPU and memory resources. There is a limit of 18 custom resource pools in addition to the two resource pools created when SQL Server 2008 is installed: INTERNAL: Use for SQL Server internal system processes  DEFAULT: Used by workloads unassigned to any workload group  598 Chapter13•PerformanceTuning The combination of minimum values across all pools cannot exceed 100% and the maximum value can be anywhere between the minimum value and 100%. In addition to Min and Max settings, Resource pools have two further calculated val- ues; Effective Maximum and Shared % (see Table 13.10). The Effective Maximum is determined by calculating the max value of a Resource pool and the minimum values of all other Resource pools. The internal pool has highest priority of all Resource pools since this is where internal processes are handled; it is not exposed to effective or share maximums. Resource Pool Min % Max % Calculated Effective Max % Calculated Shared % Effective Max Calculation Explained Shared % Calculation Explained Internal 0 100 100 0 Not applicable to internal pool Not applicable to internal pool Default 0 100 50 50 min(100, 100–50) = 50 50–0=50 Pool-A 10 100 60 50 min(100, 100–40) = 60 60–10=50 Pool-B 35 90 85 10 min(90, 100–15) = 85 85–35=10 Pool-C 5 70 55 50 min(80, 100–45) = 55 55–5=50 Table 13.10 Resource Pool Calculated Values The following T-SQL can be used to create two resource pools, the first for lecturers and the second for students: CREATERESOURCEPOOLrscpLecturers WITH (MAX_CPU_PERCENT=100,  MIN_CPU_PERCENT=50) GO CREATERESOURCEPOOLrscpStudents WITH PerformanceTuning•Chapter13 599 (MAX_CPU_PERCENT=50, MIN_CPU_PERCENT=0) GO Workload Groups The Workload Group makes managing the Resource Governor easier. The Workload Group makes it easier to assign user session requests to a specific resource pool. Workload groups also make it easier to monitor resource consumption within each Resource pool. Workload groups may be moved between Resource pools by the administrator if a particular Resource pool becomes too busy or overloaded. Similar to Resource pools, administrators can create their own Workload Groups and there are two groups created when SQL Server is installed: INTERNAL: Use for internal SQL Server operations  DEFAULT: All unassigned session requests are serviced by this  workload group Here’s the T-SQL required to create a group for two workload groups: CREATEWORKLOADGROUPgrpLecturers WITH (IMPORTANCE=MEDIUM) CREATEWORKLOADGROUPgrpStudents WITH (IMPORTANCE=LOW) Classification Function The classification function is created to identify incoming requests to SQL Server and map these incoming requests to a workload group. The classification function is a user-defined function (UDF) and is created as a scalar valued function. The function can use any valid property to classify a new session, such as Username, Hostname, or IP address. Only one UDF can be designated as a classifier at any one time. Consider performance of the UDF when creating the function since it will be used to evaluate every incoming session. The Dedicated Administrator Connection (DAC) is not exposed to classification; as such the DAC can be used to trouble- shoot performance problems relating to classification. Once the classifier function has been defined, it should be assigned to the Resource Governor, followed by the reconfigure statement: 600 Chapter13•PerformanceTuning ALTER RESOURCE GOVERNOR WITH (CLASSIFIER_FUNCTION = dbo.func_Session_Classifier) Configuring&Implementing… AlwaysEnableDAC WhenUsingResourceGovernor All new sessions are subject to the classification function. Enable Dedicated Admin Connection to provide access for troubleshooting since this connection is not subject to classification. Validate Configuration The Resource Governor should be enabled before use (is disabled by default). Configuration changes can be made dynamically and don’t require a service restart, however the following instruction should be used after any changes to bring these into effect: ALTER RESOURCE GOVERNOR RECONFIGURE Use the following DYNAMIC Management Views (DMVs) to verify configuration is as intended: sys.dm_resource_governor_resource_pools sys.dm_resource_governor_workload_groups Resource Governor Summary The Resource Governor is an important new feature to manage resource allocation among groups of users. The following simplified pseudo-steps illustrate the process an incoming session steps through in order to be allocated resources by the governor: 1. Session begins. 2. Classification function executes. 3. Workload Group membership determined; otherwise use Default. 4. Query executes within specified resource pool. PerformanceTuning•Chapter13 601 Summary of Exam Objectives This chapter provided an overview of performance tuning in SQL Server 2008, including an introduction to tracing with SQL profiler, an overview of locking and blocking, the basics of Dynamic Management Views and Performance Data Collection. Additionally we looked at how the Resource Governor can be used to manage mixed workloads to ensure minimum resource availability. We also looked at table partitioning – a technology useful when maintenance (backup, reindexing, checkdb) become cumbersome with particularly large tables. Partitioning provides the option to separate a large table into a number of smaller tables – which is completely transparent to the application. Exam Objectives Fast Track Tracing Use SQL Profiler to capture the statements being executed on a server for Ü performance review/ analysis. There can be an overhead with running traces, consider how many events Ü you capture, any filters you apply and where the trace is run. Trace data saved directly to a database or to a file then imported into a Ü database for easier analysis. Locks, Blocking, and Deadlocks Locking and blocking is normal in a database – but if frequency is excessive Ü they can lead to performance problems. Deadlocks are always damaging for performance – use SQL Profiler to Ü capture a trace or enable traceflag 1222 for more details about the processes involved in deadlocking, then address the cause. Consider the transaction isolation level and indexing to ensure processes Ü use appropriate locking mechanisms based on their requirements. Guide to the Dynamic Management Views DMVs and Dynamic Management Functions (DMFs) provide a view on Ü SQL Server internals and can be used for troubleshooting and fault diagnosis. . another user or process requires the resource (memory or CPU). This section introduces each concept and uses an example to illustrate the purpose and implementation of the concept. The example. and memory resources. There is a limit of 18 custom resource pools in addition to the two resource pools created when SQL Server 2008 is installed: INTERNAL: Use for SQL Server internal system. created when SQL Server is installed: INTERNAL: Use for internal SQL Server operations  DEFAULT: All unassigned session requests are serviced by this  workload group Here’s the T -SQL required