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Anil Desai http://AnilDesai.net Austin CodeCamp 2010 Anil Desai ◦ Independent consultant (Austin, TX) ◦ Author of numerous IT books ◦ Instructor, “Implementing and Managing SQL Server 2005” (Keystone Learning) ◦ Info: http://AnilDesai.net or [email protected] I. Performance Monitoring Overview II. Monitoring Database Servers III. Using SQL Profiler IV. Using the Database Engine Tuning Advisor V. Application Design Tips VI. Managing Processes, Locking, and Deadlocks Developing processes and approaches for performance optimization Establish a baseline Repeat (if desired) Measure performance Identify bottlenecks Make one change at a time Best Practices: ◦ Optimize for real-world workloads ◦ Monitor/review performance regularly ◦ Focus on specific issues System/OS SQL Server QueryLevel Activity Monitor Windows Performance Monitor Database Engine Tuning Advisor SQL Profiler / SQL Trace Database Engine Tuning Advisor Alerts (PerformanceBased) Query Execution Plans Dynamic Management Views (DMVs) Server-Level Issues • Users are reporting database timeouts • Intermittent transaction timeouts • “The server/application seem sluggish” ApplicationSpecific Issues • “Application A is running more slowly than usual” • “The End-of-Month report is taking too long to run.” Other Issues • Ad-hoc reports are running slowly • CPU, memory, disk, or network alerts are being generated Using SQL Server tools and features to monitor database activity Available in all current versions of Windows Statistics are organized into: ◦ Objects ◦ Counters ◦ Instances Data Collector Sets ◦ Windows Vista / Windows 7 / Windows Server 2008 ◦ Used to report on performance data that is collected over time ◦ Includes built-in System Diagnostics and System Performance collectors and reports Backup Device General Statistics Latches Locks Memory Manager Replication SQL Statistics ◦ Device throughput Bytes/sec Buffer Manager ◦ Buffer cache hit ratio ◦ Page reads / sec Buffer Partition ◦ Free Pages Cache Manager ◦ Cache Hit Ratio Databases ◦ ◦ ◦ ◦ ◦ Active Transactions Data File Size Log Growths Percent Log Used Transactions / sec ◦ Logins | logouts / sec ◦ User Connections ◦ Latch waits / sec ◦ Lock requests / sec ◦ Lock waits / sec ◦ Everything! ◦ Depends on configuration ◦ Batch requests / sec ◦ SQL compilations / sec Anil Desai 10 SQL Server Activity Monitor ◦ Provides a quick overview of database server activity ◦ CPU, Processes, Resource Waits and Disk I/O ◦ “Recent Expensive Queries” SQL Server Management Studio Reports ◦ Quick overview of SQL Server usage ◦ Can export to Excel or PDF Server Dashboard Memory Consumption Activity – All Block Transactions Activity – Top Sessions Performance – Batch Execution Statistics Performance – Top Queries by Average CPU Object Execution Statistics Server-Level Reports Disk Usage All Transactions All Blocking Transactions Index Usage Statistics Top Transactions by Age Schema Changes History Database-Level Reports Windows Event Logs / Event Viewer ◦ Application and System Event Logs SQL Server Management Studio ◦ SQL Server Logs Can configure max. # of log files ◦ SQL Server Agent Error logs Can configure logging levels (Errors, Warnings, Information) Using the Log File Viewer ◦ Can Export / Load log information ◦ Can search for specific errors/messages Purpose: ◦ Monitoring and troubleshooting ◦ View server state and performance details ◦ Returns relational result sets (use standard SELECT statements) Full list can be viewed in “Views System Views” section of the properties of the database Scopes: ◦ Server level ◦ Database level Query Execution / Processes •sys.dm_exec_requests Storage Engine •sys.DM_DB_File_Space_Usage Indexes •sys.DM_DB_Index_Operational_Stats •sys.DM_DB_Index_Physical_Stats Disk I/O •sys.DM_IO_Pending_IO_Requests •sys.DM_IO_Virtual_File_Stats Other Categories • Schema information | Common Language Runtime (CLR) • Database Mirror / Clustering | Replication Data Collected: ◦ System Information (MSINFO) ◦ Windows Event Logs ◦ SQL Server configuration Command-Line Utility (SQLDiag.exe) ◦ ◦ ◦ ◦ Stores output to files Configuration file: SQLDiag.xml Can run as a service (/R) Can run in continuous mode Monitoring SQL Server Activity Purpose / Features: ◦ ◦ ◦ ◦ ◦ ◦ ◦ GUI for managing SQL Trace Monitor important events Capture performance data / resource usage Replaying of workloads / transactions Identifying performance bottlenecks Correlation of data with System Monitor Workloads for Database Tuning Advisor Examples: ◦ Generate a list of the 100 slowest queries ◦ Monitor all failed logins (Security) SQL Profiler Terminology ◦ ◦ ◦ ◦ Trace Definitions Events Columns Filters Creating and Managing SQL Traces ◦ SQL Profiler (GUI) ◦ System Stored Procedures (Transact-SQL) Trace Templates (Built-In) ◦ Standard (Default), SP_Counts ◦ TSQL, TSQL_Duration, TSQL_Grouped,TSQL_Replay, TSQL_SPs ◦ Tuning Trace Trace File Trace Table Trace Template ◦ A set of events, data columns and filters that specify what data should be collected ◦ Data can be saved to a file or a database table ◦ Trace data that is saved to a binary file ◦ Default extension is “.trc” ◦ A SQL Server database table in which trace information is stored ◦ Profiler will automatically create the structure of this table when you start running a new trace ◦ Saved specifications that can be used as the basis for new traces ◦ E.g., an environment may have a “Security Monitoring template”, a “CRM Application Performance”, etc. ◦ Default extension is “.tdf” 20 Anil Desai Groupings: ◦ Event Categories ◦ Event Classes ◦ Events Examples: ◦ ◦ ◦ ◦ ◦ TSQL Stored Procedures Performance Errors and Warnings Security auditing Event Categories Event Classes Events Specifies the details to be monitored/recorded Configuring columns ◦ Columns can be ordered and grouped ◦ Values can be filtered Examples of Columns: ◦ ◦ ◦ ◦ ◦ StartTime / EndTime TextData Duration Resource Usage (CPU, Reads, Writes) Information: User, Database, App. Names Interactive ◦ Good for “live” monitoring of small sets of data Trace Files (*.trc) ◦ Can enable file rollover based on size ◦ “Server processes trace data” option Trace table ◦ Will automatically create the table ◦ Can set maximum number of rows Scheduling of traces (stop time) Launching SQL Profiler Connecting to a database instance Configuring output options Create a trace definition Specifying events, columns, and filters Running and viewing a trace Creating new templates using SQL Profiler Scripting trace definitions ◦ ◦ ◦ ◦ ◦ sp_trace_create sp_trace_setfilter sp_trace_GenerateEvent sp_trace_SetEvent sp_trace_SetStatus Extracting SQL Server Events ◦ Transact-SQL Events ◦ ShowPlan Events ◦ Deadlock Events Purpose / Goal: ◦ Correlate server performance with database performance Process: ◦ Define and start a counter log ◦ Define and start a SQL Profiler trace ◦ Import Performance Data in SQL Profiler Required Trace properties ◦ StartTime ◦ EndTime Analyzing workloads to optimize physical database structures Reviews sample workloads and makes performance recommendations Evaluates Physical Design Structures (PDS) ◦ Indexes (clustered, non-clustered) ◦ Indexed Views ◦ Partitions Numerous analysis options Output ◦ Generates modification scripts ◦ Generates Reports for later analysis Files ◦ Transact-SQL Files ◦ XML Files ◦ Should represent commonly-used queries SQL Profiler Trace Files / Tables ◦ Use Tuning built-in trace template ◦ Events: Transact-SQL Batch Remote Procedure Call (RPC) ◦ Columns: Event Class and Text Data Limit tuning time Tuning Options ◦ ◦ ◦ ◦ ◦ Allowed Physical Design Structures (PDS) Keep all/specific existing objects Maximum storage space Online or offline recommendations Partitioning Reports can be exported to XML files Report Examples: Workload analysis Column access Statement cost Table access Event frequency View-Table Relations Index Usage (current / recommended) Process: ◦ ◦ ◦ ◦ ◦ Generate a workload (file or table) Select tuning options Run the analysis View reports Save and/or apply recommendations Running the DTA: ◦ Database Engine Tuning Advisor Application (GUI) ◦ Dta.exe command-line utility Practical ways to improve database application performance Create an abstraction layer between the database and the presentation code ◦ Separates presentation and logic (esp. in Web Apps) ◦ Example: ADO.NET Datasets Database design: ◦ Understand typical use-cases before designing the database ◦ Create and enforce naming conventions ◦ Balance write (OLTP) and read (reporting) performance requirements ◦ Use strategic denormalization 34 Anil Desai Never include actions that require user input within a transaction Use connection pooling, whenever possible ◦ Open connections late and close them early ◦ Avoid unnecessary server round-trips Use client-side caching whenever possible ◦ Optimistic concurrency ◦ Pessimistic concurrency Distribute processing ◦ Some operations are more efficient on the DB server (e.g., aggregations, sorting, etc.) Troubleshooting common SQL Server performance problems Processes ◦ Interactive users SQL Server Management Studio ◦ Applications (Connection Pooling) SQL Profiler Database Engine Tuning Advisor Replication Service Broker Process IDs < 50 are system-related SQL Server Activity Monitor ◦ ◦ ◦ ◦ Processes (connected users) Locks (by Process / by Object) Filtering options Auto-refresh option System Stored Procedures / Views ◦ ◦ ◦ ◦ Sys.DM_Exec_Sessions Sys.DM_Exec_Requests Sys.SysProcesses sp_who / sp_who2 Process Information ◦ Current Process ID: @@SPID ◦ Session Options: DBCC USEROPTIONS Killing Processes ◦ KILL ProcessID [WITH STATUSONLY] Viewing Last Activity ◦ DBCC INPUTBUFFER(ProcessID) ◦ DBCC OUTPUTBUFFER(ProcessID) Coordinates multiple accesses to the same data Ensures ACID Properties for transactions (Atomic, Consistent, Independent, Durable) Contention can reduce performance Locking granularity: ◦ Row-Level, Page-Level, Table-Level, etc. Lock Modes: ◦ Shared, Exclusive, etc. Lock escalation Blocking ◦ When transaction(s) must wait for a lock on a resource ◦ LOCK_TIMEOUT setting (default = wait forever) Locking Models: ◦ Pessimistic ◦ Optimistic Balance of concurrency (performance) vs. consistency ◦ Affects SELECT queries ◦ SET TRANSACTION ISOLATION LEVEL Transaction Isolation Levels ◦ ◦ ◦ ◦ ◦ READ UNCOMMITTED READ COMMITTED (default) REPEATABLE READ SERIALIZABLE SNAPSHOT Row-Versioning: ◦ ALLOW_SNAPSHOT_ISOLATION ◦ READ_COMMITTED_SNAPSHOT Activity Monitor SQL Profiler ◦ Locks Event Category System Monitor: ◦ SQL Server Locks Object System Views ◦ Sys.DM_Tran_Locks ◦ Sys.DM_Exec_Requests System Stored Procedures ◦ sp_Lock Deadlocks: Deadlock victim Example: ◦ Two or more tasks permanently block each other based on resource locks ◦ Default resolution is within 5 seconds ◦ Transaction is rolled-back ◦ Process receives a 1205 error ◦ Process 1 locks the Customers table and requires access to the Orders Table ◦ Process 2 locks the Orders table and requires access to the Customers Table Minimize transaction times ◦ Commit / Rollback transactions as quickly as possibly ◦ Avoid user-related time within a transaction Access objects in a consistent order Change the transaction isolation level ◦ Use a lower level isolation level, if appropriate ◦ Use snapshot-based isolation levels Deadlock priorities: ◦ SET DEADLOCK_PRIORITY (LOW, NORMAL, HIGH, integer) Deadlock resolution: ◦ Lower priority is killed first ◦ If equal priorities, least expensive transaction becomes the victim ◦ Application or user should attempt to re-run the transaction SQL Server Error Log SQL Profiler ◦ Locks Event Category Lock:Deadlock Chain Lock:Deadlock Deadlock Graph ◦ Events Extraction Trace Property ◦ Export deadlock XML (.xdl) file Viewing Deadlock Files ◦ SQL Server Management Studio (File Open SQL Deadlock Files (*.xdl) For more information: http://AnilDesai.net [email protected]
