Performance tuning in sql server
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Performance tuning in sql server Performance tuning in sql server Presentation Transcript

  • Performance Tuning in SQL Server Antonios Chatzipavlis Software Architect , Development Evangelist, IT Consultant MCT, MCITP, MCPD, MCSD, MCDBA, MCSA, MCTS, MCAD, MCP, OCA 1
  • Objectives • • • • • Why is Performance Tuning Necessary? How to Optimize SQL Server for performance How to Optimize Database for performance How to Optimize Query for performance Define and implement monitoring standards for database servers and instances • How to troubleshoot SQL Server 2
  • Performance Tuning in SQL Server Why is performance tuning necessary? 3 View slide
  • Why is Performance Tuning Necessary? • Allowing your system to scale • Adding more customers • Adding more features • Improve overall system performance • Save money but not wasting resources • The database is typically one of the most expensive resources in a datacenter 4 View slide
  • General Scaling Options Scaling SQL Server with Bigger Hardware • • • • Purchase a larger server, and replace the existing system. Works well with smaller systems. Cost prohibitive for larger systems. Can be a temporary solution. 5
  • General Scaling Options Scaling SQL Server with More Hardware • Purchase more hardware and split or partition the database. • Partitioning can be either vertical or horizontal • Vertical: Split the databases based on a specific demographic such as time zone or zip code. • Horizontal: Split components out of one database into another 6
  • General Scaling Options Scaling SQL Server without adding hardware • • • • • • • • Adjusting and rewriting queries. Adding indexes. Removing indexes. Re-architecting the database schema. Moving things that shouldn’t be in the database. Eliminating redundant work on the database. Caching of data. Other performance tuning techniques. 7
  • 1. Database Partitioning 8
  • Performance Tuning in SQL Server How to Optimize SQL Server for performance 9
  • Performance Factors • • • • • CPU Memory IO Network TempDB 10
  • CPU and SQL Server • CPU Intensive Operations • Compression • Bulk Load operations • Compiling or Recompiling Queries • Hyper-Threading • Is just 1.3 times better than non hyper-threaded execution • The currently accepted best practice recommendation is that you should run SQL Server with Hyper-Threading disabled • L3 Cache 11
  • CPU and SQL Server Performance Counters Counter Description Guidelines Processor:% Processor Time This counter monitors the amount of time the CPU spends executing a thread that is not idle A consistent state of 80 percent to 90 percent may indicate the need to upgrade your CPU or add more processors. System: %Total Processor To determine the average for all processors Processor: % Privileged Time Corresponds to the percentage of time the processor spends on execution of Microsoft Windows kernel commands, such as processing of SQL Server I/O requests. Processor: %User Time Corresponds to the percentage of time that the processor spends on executing user processes such as SQL Server. System: Processor Queue Length Corresponds to the number of threads waiting for processor time. A processor bottleneck develops when threads of a process require more processor cycles than are available. If this counter is consistently high when the Physical Disk counters are high, consider installing a faster or more efficient disk subsystem. If more than a few processes attempt to utilize the processor's time, you might need to install a faster processor. Or, if you have a multiprocessor system, you could add a processor. 12
  • Memory and SQL Server Enable Address Windowing Extensions (AWE) • Tuning 32-bit Systems • Use /PAE and /3GB Together (Windows 2003) • Running BCDEDIT /set increaseUserVA 3072 (Windows 2008) • Tuning 64-bit Systems • If needed, enable AWE on Enterprise Edition of SQL Server • If needed, enable AWE on Standard Edition of SQL Server only when SP1 with Cumulative Update 2 applied. Read more info at http://support.microsoft.com/kb/970070 13
  • Memory and SQL Server Min and Max Server Memory • Control the allowable size of SQL Server’s buffer pool. • Do not control all of SQL Server’s memory usage, just the buffer pool. • When the SQL Server service starts, it does not acquire all the memory configured in Min Server Memory but instead starts with only the minimal required, growing as necessary. • Once memory usage has increased beyond the Min Server Memory setting, SQL Server won’t release any memory below that figure. • Max Server Memory is the opposite of Min Server Memory, setting a “ceiling” for the buffer pool 14
  • Memory and SQL Server How to configure Max Server Memory • Look at the buffer pool’s maximum usage. • Set SQL Server to dynamically manage memory • Monitor MSSQLSERVER : Memory ManagerTotal Server Memory (KB) counter using Performance Monitor • Determine the maximum potential for non-buffer pool usage. • 2GB for Windows • xGB for SQL Server worker threads • Each thread use 0.5MB on x86, 2MB on x64, and 4MB on Itanium. • 1GB for multi-page allocations, linked servers, and other consumers of memory outside the buffer pool • 1–3GB for other applications that might be running on the system, such as backup programs 15
  • Memory and SQL Server Example of Max Server Memory configuration • In 8-CPU cores and 16GB of RAM running SQL Server 2008 x64 and a third-party backup utility, you would allow the following: • • • • 2GB for Windows 1GB for worker threads (576 Χ 2MB rounded down) 1GB for MPAs, etc. 1GB for the backup program • The total is 5GB, and you would configure Max Server Memory to 11GB. 16
  • Memory and SQL Server Performance Counters Counter Description Guidelines Memory: Available Bytes Indicates how many any bytes of memory are currently available for use by Processes Low values can indicate that there is an overall shortage of memory on computer or that an application is not releasing memory Memory: Pages/sec Indicates the number of pages that either were retrieved from disk due to hard page faults or written to disk to free space in the working set due to page faults. A high rate could indicate excessive paging. Monitor the Memory: Page Faults/sec counter to make sure that the disk activity is not caused by paging. Process - Page Faults/sec (sql server instance) Windows Virtual Memory Manager takes pages from SQL Server and other processes as it trims the working-set sizes of those processes. A high number indicates excessive paging and disk thrashing. Use this counter to check whether SQL Server or another process is causing the excessive paging. SQL Server: Buffer ManagerBuffer Cache Hit Ratio Monitors the percentage of required pages found in the buffer cache, without reading from hard disk. Add more memory until the value is consistently greater than 90 percent. SQL Server: Buffer ManagerTotal Pages Monitors the total number of pages in the buffer cache, including database, free, and stolen pages from other processes. A low number may indicate frequent disk I/O or thrashing. Consider adding more memory. SQL Server: Memory ManagerTotal Server Memory (KB) Monitors the total amount of dynamic memory that the server is using. If this counter is consistently high in comparison to the amount of physical memory available, more memory may be required. 17
  • IO and SQL Server Choose the right hard disk subsystem • RAID 5 • • • • Loved by storage administrators Dominated choice for non-database applications It’s cost effective and cost efficient Minimize the space required in the datacenter (fewer drives need fewer bays) • RAID 10 • Microsoft recommendation for log files • Storage Area Networks (SANs) • Performance is not always predictable if two servers share the same drive • iSCSI Storage Area Networks • For good performance needs dedicated switches. 18
  • IO and SQL Server Choosing Which Files to Place on Which Disks • Best practices dictate that SQL Server • • • • data files, logs, tempdb files backup files are all written to separate arrays • Put log files on RAID 10 • Put data files on RAID 5 (to save money) 19
  • IO and SQL Server Using Compression to Gain Performance • Increase IO performance but has CPU penalty • The SQL Server engine has to compress the data before writing the page, and decompress the data after reading the page • However, in practice this penalty is far outweighed by the time saved waiting for storage. Read more at http://msdn.microsoft.com/en-us/library/dd894051.aspx • Example: If a 10GB index is compressed down to 3GB, then an index scan will be completed 70% faster simply because the data takes less time to read off the drives. • Is Enterprise Edition feature 20
  • IO and SQL Server Performance Counters Counter Description Guidelines % Disk Time Monitors the percentage of time that the disk is busy with read/write activity. If this counter is high (more than 90 percent), check the Current Disk Queue Length counter. Avg. Disk Queue Length Monitors the average number of read/write requests that are queued. This counter should be no more than twice the number of spindles. Current Disk Queue Length Monitors the current number of read/write requests that are queued. This counter should be no more than twice the number of spindles • Monitor the Page Faults/sec counter in the Memory object to make sure that the disk activity is not caused by paging. • If you have more than one logical partition on the same hard disk, use the Logical Disk counters rather than the Physical Disk counters. 21
  • 1. Use Performance Monitor 22
  • Performance Tuning in SQL Server How to Optimize Database for performance 23
  • Performance Optimization Model Server Tuning Locking Indexing Query Optimization Schema Design 24
  • Schema Design Optimization Normalization • In this process you organize data to minimize redundancy, which eliminates duplicated data and logical ambiguities in the database Normal Form Description First Every attribute is atomic, and there are no repeating groups Second Complies with First Normal Form, and all non-key columns depend on the whole key Third Complies with Second Normal Form, and all nonkey columns are non-transitively dependent upon the primary key 25
  • Schema Design Optimization Denormalization • In this process you re-introduce redundancy to the database to optimize performance. • When to use denormalization: • To pre-aggregate data • To avoid multiple/complex joins • When not to use denormalization: • To prevent simple joins • To provide reporting data • To prevent same row calculations 26
  • Schema Design Optimization Generalization • In this process you group similar entities together into a single entity to reduce the amount of required data access code. • Use generalization when: • A large number of entities appear to be of the same type • Multiple entities contain the same attributes • Do not use generalization when: • It results in an overly complex design that is difficult to manage 27
  • Schema Design Optimization Generalization Example 28
  • Performance Tuning in SQL Server How to Optimize Query for performance 29
  • Key Measures for Query Performance Key factors for query performance:  Resources used to execute the query  Time required for query execution SQL Server tools to measure query performance:  Performance Monitor  SQL Server Profiler 30
  • Logical Execution of Query 31
  • Logical Execution of Query Example Data customerid city Orderid customerid ANTON Athens 1 NASOS CHRIS Salonica 2 NASOS FANIS Athens 3 FANIS NASOS Athens 4 FANIS 5 FANIS 6 CHRIS 7 NULL 32
  • Logical Execution of Query Example Query & Results SELECT C.customerid, COUNT(O.orderid) AS numorders FROM dbo.Customers AS C LEFT OUTER JOIN dbo.Orders AS O ON C.customerid = O.customerid WHERE C.city = 'Athens' GROUP BY C.customerid HAVING COUNT(O.orderid) < 3 ORDER BY numorders; Customerid numorders ANTON 0 NASOS 2 33
  • Logical Execution of Query 1st Step - Cross Join FROM dbo.Customers AS C ... JOIN dbo.Orders AS O Customerid City Orderid customerid ANTON Athens 1 NASOS ANTON Athens 2 NASOS ANTON Athens 3 FANIS ANTON Athens 4 FANIS ANTON Athens 5 FANIS ANTON Athens 6 CHRIS ANTON Athens 7 NULL CHRIS Salonica 1 NASOS CHRIS Salonica 2 NASOS CHRIS Salonica 3 FANIS CHRIS Salonica 4 FANIS CHRIS Salonica 5 FANIS CHRIS Salonica 6 CHRIS CHRIS Salonica 7 NULL FANIS Athens 1 NASOS FANIS Athens 2 NASOS FANIS Athens 3 FANIS FANIS Athens 4 FANIS FANIS Athens 5 FANIS FANIS Athens 6 CHRIS FANIS Athens 7 NULL NASOS Athens 1 NASOS NASOS Athens 2 NASOS NASOS Athens 3 FANIS NASOS Athens 4 FANIS NASOS Athens 5 FANIS NASOS Athens 6 CHRIS NASOS Athens 7 NULL 34
  • Logical Execution of Query 2nd Step- Apply Join condition ON Filter ON C.customerid = O.customerid Customerid City Orderid customerid ΟΝ Filter ANTON Athens 1 NASOS FALSE ANTON Athens 2 NASOS FALSE ANTON Athens 3 FANIS FALSE ANTON Athens 4 FANIS FALSE ANTON Athens 5 FANIS FALSE ANTON Athens 6 CHRIS FALSE ANTON Athens 7 NULL UNKNOWN CHRIS Salonica 1 NASOS FALSE CHRIS Salonica 2 NASOS FALSE CHRIS Salonica 3 FANIS FALSE CHRIS Salonica 4 FANIS FALSE CHRIS Salonica 5 FANIS FALSE CHRIS Salonica 6 CHRIS TRUE CHRIS Salonica 7 NULL UNKNOWN FANIS Athens 1 NASOS FALSE FANIS Athens 2 NASOS FALSE FANIS Athens 3 FANIS TRUE FANIS Athens 4 FANIS TRUE FANIS Athens 5 FANIS TRUE FANIS Athens 6 CHRIS FALSE FANIS Athens 7 NULL UNKNOWN NASOS Athens 1 NASOS TRUE NASOS Athens 2 NASOS TRUE NASOS Athens 3 FANIS FALSE NASOS Athens 4 FANIS FALSE NASOS Athens 5 FANIS FALSE NASOS Athens 6 CHRIS FALSE NASOS Athens 7 NULL UNKNOWN Customerid City Orderid customerid CHRIS Salonica 6 CHRIS FANIS Athens 3 FANIS FANIS Athens 4 FANIS FANIS Athens 5 FANIS NASOS Athens 1 NASOS NASOS Athens 2 NASOS 35
  • Logical Execution of Query 3rd Step - Apply OUTER Join FROM dbo.Customers AS C LEFT OUTER JOIN dbo.Orders AS O Customerid City Orderid customerid CHRIS Salonica 6 CHRIS FANIS Athens 3 FANIS FANIS Athens 4 FANIS FANIS Athens 5 FANIS NASOS Athens 1 NASOS NASOS Athens 2 NASOS ΑΝΤΟΝ Athens NULL NULL 36
  • Logical Execution of Query 4th Step - Apply WHERE filter WHERE C.city = 'Athens' Customerid City Orderid customerid FANIS Athens 3 FANIS FANIS Athens 4 FANIS FANIS Athens 5 FANIS NASOS Athens 1 NASOS NASOS Athens 2 NASOS ΑΝΤΟΝ Athens NULL NULL 37
  • Logical Execution of Query 5th Step - Apply Grouping GROUP BY C.customerid Customerid City Orderid customerid FANIS Athens 3 FANIS FANIS Athens 4 FANIS FANIS Athens 5 FANIS NASOS Athens 1 NASOS NASOS Athens 2 NASOS ΑΝΤΟΝ Athens NULL NULL 38
  • Logical Execution of Query 6th Step - Apply Cube or Rollup 39
  • Logical Execution of Query 7th Step - Apply HAVING Filter HAVING COUNT(O.orderid) < 3 Customerid City Orderid customerid NASOS Athens 1 NASOS NASOS Athens 2 NASOS ΑΝΤΟΝ Athens NULL NULL 40
  • Logical Execution of Query 8th Step - Apply SELECT List SELECT C.customerid, COUNT(O.orderid) AS numorders Customerid numorders NASOS 2 ANTON 0 41
  • Logical Execution of Query 9th Step - Apply DISTINCT 42
  • Logical Execution of Query 10th Step - Apply ORDER BY ORDER BY numorders Customerid numorders ANTON 0 NASOS 2 43
  • Logical Execution of Query 11th Step - Apply TOP 44
  • Logical Execution of Query Get the Result Customerid numorders ANTON 0 NASOS 2 45
  • Performance Tuning in SQL Server How to Optimize Query for performance Top 10 for Building Efficient Queries 46
  • Top 10 for Building Efficient Queries 1.Favor set-based logic over procedural or cursor logic • The most important factor to consider when tuning queries is how to properly express logic in a set-based manner. • Cursors or other procedural constructs limit the query optimizer’s ability to generate flexible query plans. • Cursors can therefore reduce the possibility of performance improvements in many situations 47
  • Top 10 for Building Efficient Queries 2.Test query variations for performance • The query optimizer can often produce widely different plans for logically equivalent queries. • Test different techniques, such as joins or subqueries, to find out which perform better in various situations. 48
  • Top 10 for Building Efficient Queries 3.Avoid query hints. • You must work with the SQL Server query optimizer, rather than against it, to create efficient queries. • Query hints tell the query optimizer how to behave and therefore override the optimizer’s ability to do its job properly. • If you eliminate the optimizer’s choices, you might limit yourself to a query plan that is less than ideal. • Use query hints only when you are absolutely certain that the query optimizer is incorrect. 49
  • Top 10 for Building Efficient Queries 4.Use correlated subqueries to improve performance. • Since the query optimizer is able to integrate subqueries into the main query flow in a variety of ways, subqueries might help in various query tuning situations. • Subqueries can be especially useful in situations in which you create a join to a table only to verify the existence of correlated rows. For better performance, replace these kinds of joins with correlated subqueries that make use of the EXISTS operator --Using a LEFT JOIN SELECT a.parent_key FROM parent_table a LEFT JOIN child_table b ON a.parent_key = b.parent_key WHERE B.parent_key IS NULL --Using a NOT EXISTS SELECT a.parent_key FROM parent_table a WHERE NOT EXISTS (SELECT * FROM child_table b WHERE a.parent_key =b.parent_key) 50
  • Top 10 for Building Efficient Queries 5. Avoid using a scalar user-defined function in the WHERE clause. • Scalar user-defined functions, unlike scalar subqueries, are not optimized into the main query plan. • Instead, you must call them row-by-row by using a hidden cursor. • This is especially troublesome in the WHERE clause because the function is called for every input row. • Using a scalar function in the SELECT list is much less problematic because the rows have already been filtered in the WHERE clause. 51
  • Top 10 for Building Efficient Queries 6.Use table-valued user-defined functions as derived tables. • In contrast to scalar user-defined functions, table-valued functions are often helpful from a performance point of view when you use them as derived tables. • The query processor evaluates a derived table only once per query. • If you embed the logic in a table-valued user-defined function, you can encapsulate and reuse it for other queries. CREATE FUNCTION Sales.fn_SalesByStore (@storeid int) RETURNS TABLE AS RETURN ( SELECT P.ProductID, P.Name, SUM(SD.LineTotal) AS 'YTD Total‘ FROM Production.Product AS P JOIN Sales.SalesOrderDetail AS SD ON SD.ProductID = P.ProductID JOIN Sales.SalesOrderHeader AS SH ON SH.SalesOrderID = SD.SalesOrderID WHERE SH.CustomerID = @storeid GROUP BY P.ProductID, P.Name ) 52
  • Top 10 for Building Efficient Queries 7.Avoid unnecessary GROUP BY columns • Use a subquery instead. • The process of grouping rows becomes more expensive as you add more columns to the GROUP BY list. • If your query has few column aggregations but many nonaggregated grouped columns, you might be able to refactor it by using a correlated scalar subquery. • This will result in less work for grouping in the query and therefore possibly better overall query performance. SELECT p1.ProductSubcategoryID, p1.Name FROM Production.Product p1 WHERE p1.ListPrice > ( SELECT AVG (p2.ListPrice) FROM Production.Product p2 WHERE p1.ProductSubcategoryID = p2.ProductSubcategoryID) 53
  • Top 10 for Building Efficient Queries 8.Use CASE expressions to include variable logic in a query • The CASE expression is one of the most powerful logic tools available to T-SQL programmers. • Using CASE, you can dynamically change column output on a row-by-row basis. • This enables your query to return only the data that is absolutely necessary and therefore reduces the I/O operations and network overhead that is required to assemble and send large result sets to clients. 54
  • Top 10 for Building Efficient Queries 9. Divide joins into temporary tables when you query very large tables. • The query optimizer’s main strategy is to find query plans that satisfy queries by using single operations. • Although this strategy works for most cases, it can fail for larger sets of data because the huge joins require so much I/O overhead. • In some cases, a better option is to reduce the working set by using temporary tables to materialize key parts of the query. You can then join the temporary tables to produce a final result. • This technique is not favorable in heavily transactional systems because of the overhead of temporary table creation, but it can be very useful in decision support situations. 55
  • Top 10 for Building Efficient Queries 10. Refactoring Cursors into Queries. • Rebuild logic as multiple queries • Rebuild logic as a user-defined function • Rebuild logic as a complex query with a case expression 56
  • 1. Query optimization 2. Cursor refactoring 58
  • Performance Tuning in SQL Server Best Practices for Stored Procedures and Views 59
  • Stored Procedures Best Practices • Avoid using “sp_” as name prefix • Avoid stored procedures that accept parameters for table names • Use the SET NOCOUNT ON option in stored procedures • Limit the use of temporary tables and table variables in stored procedures • If a stored procedure does multiple data modification operations, make sure to enlist them in a transaction. • When working with dynamic T-SQL, use sp_executesql instead of the EXEC statement 60
  • Views Best Practices • • • • • Use views to abstract complex data structures Use views to encapsulate aggregate queries Use views to provide more user-friendly column names Think of reusability when designing views Avoid using the ORDER BY clause in views that contain a TOP 100 PERCENT clause. • Utilize indexes on views that include aggregate data 61
  • Performance Tuning in SQL Server Optimizing an Indexing Strategy 62
  • Index Architecture Clustered Nonclustered 63
  • Types of Indexes • Clustered • Nonclustered • Unique • Index with included column • Indexed view • Full-text • XML 64
  • Guidelines for designing indexes • Examine the database characteristics. For example, your indexing strategy will differ between an online transaction processing system with frequent data updates and a data warehousing system that contains primarily read-only data. • Understand the characteristics of the most frequently used queries and the columns used in the queries. For example, you might need to create an index on a query that joins tables or that uses a unique column for its search argument. • Decide on the index options that might enhance the performance of the index. Options that can affect the efficiency of an index include FILLFACTOR and ONLINE. • Determine the optimal storage location for the index. You can choose to store a nonclustered index in the same filegroup as the table or on a different filegroup. If you store the index in a filegroup that is on a different disk than the table filegroup, you might find that disk I/O performance improves because multiple disks can be read at the same time. • Balance read and write performance in the database. You can create many nonclustered indexes on a single table, but it is important to remember that each new index has an impact on the performance of insert and update operations. This is because nonclustered indexes maintain copies of the indexed data. Each copy of the data requires I/O operations to maintain it, and you might cause a reduction in write performance if the database has to write too many copies. You must ensure that you balance the needs of both select queries and data updates when you design an indexing strategy. • Consider the size of tables in the database. The query processor might take longer to traverse the index of a small table than to perform a simple table scan. Therefore, if you create an index on a small table, the processor might never use the index. However, the database engine must still update the index when the data in the table changes. • Consider the use of indexed views. Indexes on views can provide significant performance gains when the view contains aggregations, table joins, or both. 65
  • Nonclustered Index do’s & don’ts • Create a nonclustered index for columns used for: • Predicates • Joins • Aggregation • Avoid the following when designing nonclustered indexes: • Redundant indexes • Wide composite indexes • Indexes for one query • Nonclustered indexes that include the clustered index 66
  • Clustered Indexes do’s & don’ts • Use clustered indexes for: • Range queries • Primary key queries • Queries that retrieve data from many columns • Do not use clustered indexes for: • Columns that have frequent changes • Wide keys 67
  • 1. Database Engine Tuning Advisor 68
  • Performance Tuning in SQL Server Define and implement monitoring standards for database servers and instances 69
  • Monitoring Stages Stage 1 Monitoring the database environment Narrowing down a performance issue to a particular database environment area Stage 2 Stage 3 Narrowing down a performance issue to a particular database environment object Stage 4 Stage 5 Troubleshooting individual problems Implementing a solution 70
  • Monitoring the database environment • You must collect a broad range of performance data. • The monitoring system must provide you with enough data to solve the current performance issues. • You must set up a monitoring solution that collects data from a broad range of sources. • Active data, you can use active collection tools • System Monitor, • Error Logs, • SQL Server Profiler • Inactive data you can use sources • Database configuration settings, • Server configuration settings, • Metadata from SQL Server installation and databases 71
  • Guidelines for Auditing and Comparing Test Results • Scan the outputs gathered for any obvious performance issues. • Automate the analysis with the use of custom scripts and tools. • Analyze data soon after it is collected. • Performance data has a short life span, and if there is a delay, the quality of the analysis will suffer. • Do not stop analyzing data when you discover the first set of issues. • Continue to analyze until all performance issues have been identified. • Take into account the entire database environment when you analyze performance data. 73
  • Monitoring Tools • • • • • • • SQL Server Profiler System Monitor SQLDIAG DMVs for Monitoring Performance Data Collector SQLNexus (CodePlex) SQLIO 74
  • SQL Server Profiler guidelines • Schedule data tracing for peak and nonpeak hours • Use Transact-SQL to create your own SQL Server Profiler traces to minimize the performance impact of SQL Server Profiler. • Do not collect the SQL Server Profiler traces directly into a SQL Server table. • After the trace has ended, use fn_trace_gettable function to load the data into a table. • Store collected data on a computer that is not the instance that you are tracing. 75
  • System Monitor guidelines • Execute System Monitor traces at different times during the week, month. • Collect data every 36 seconds for a week. • If the data collection period spans more than a week, set the collection time interval in the range of 300 to 600 seconds. • Collect the data in a comma-delimited text file. You can load this text file into SQL Server Profiler for further analysis. • Execute System Monitor on one server to collect the performance data of another server. 76
  • DMVs for Monitoring DMV Description sys.dm_os_threads Returns a list of all SQL Server Operating System threads that are running under the SQL Server process. sys.dm_os_memory_pools Returns a row for each object store in the instance of SQL Server. You can use this view to monitor cache memory use and to identify bad caching behavior sys.dm_os_memory_cache_counters Returns a snapshot of the health of a cache, provides runtime information about the cache entries allocated, their use, and the source of memory for the cache entries. sys.dm_os_wait_stats Returns information about all the waits encountered by threads that executed. You can use this aggregated view to diagnose performance issues with SQL Server and also with specific queries and batches. sys.dm_os_sys_info Returns a miscellaneous set of useful information about the computer, and about the resources available to and consumed by SQL Server. 77
  • Performance Data Collector • Management Data Warehouse • Performance Data Collection • • • • Performance data collection components System collection sets User-defined collection sets Reporting • Centralized Administration: Bringing it all together Performance Data Collection and Reporting 78
  • 1. Resource Governor 2. SQL Server Profiler (if time permits) 79
  • Performance Tuning in SQL Server Troubleshoot SQL Server concurrency issues 80
  • Transaction Isolation Levels • Read uncommitted • Read committed • Repeatable read • Snapshot • Serializable 81
  • Reduce Locking and Blocking Guidelines • Keep logical transactions short • Avoid cursors • Use efficient and well-indexed queries • Use the minimum transaction isolation level required • Keep triggers to a minimum 82
  • Minimizing Deadlocks • • • • • Access objects in the same order. Avoid user interaction in transactions. Keep transactions short and in one batch. Use a lower isolation level. Use a row versioning–based isolation level. • Set the READ_COMMITTED_SNAPSHOT database option ON to enable read-committed transactions to use row versioning. • Use snapshot isolation. • Use bound connections. • Allow two or more connections to share the same transaction and locks. • Can work on the same data without lock conflicts. • Can be created from multiple connections within the same application, or from multiple applications with separate connections. • Make coordinating actions across multiple connections easier. • http://msdn.microsoft.com/en-us/library/aa213063(SQL.80).aspx 83
  • SQLschool.gr • A dream • Reliable source of knowledge for SQL Server • http://www.autoexec.gr/blogs/antonch 84
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