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Practical SQL Server Performance Monitoring & Optimization
Anil Desaihttp://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]
Speaker Information
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
Agenda and Overview
Performance Monitoring Overview
Developing processes and approaches for performance optimization
Best Practices:◦ Optimize for real-
world workloads
◦ Monitor/review performance regularly
◦ Focus on specific issues
Performance Monitoring Approaches
Establish a baseline
Identify bottlenecks
Make one change at a time
Measure performance
Repeat (if desired)
Overview of Performance Monitoring Tools and Methods
System/OS
Windows Performance Monitor
Alerts (Performance-Based)
SQL ServerActivity Monitor
SQL Profiler / SQL Trace
Database Engine Tuning Advisor
Dynamic Management Views (DMVs)
Query-Level
Database Engine Tuning Advisor
Query Execution Plans
Monitoring and Troubleshooting Scenarios
Server-Level Issues
• Users are reporting database timeouts• Intermittent transaction timeouts• “The server/application seem sluggish”
Application-Specific
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
Monitoring SQL ServerUsing 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
Windows Performance Monitor
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Backup Device◦ 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
Useful SQL Server Performance Counters
General Statistics◦ Logins | logouts / sec◦ User Connections
Latches◦ Latch waits / sec
Locks◦ Lock requests / sec◦ Lock waits / sec
Memory Manager◦ Everything!
Replication◦ Depends on configuration
SQL Statistics◦ Batch requests / sec◦ SQL compilations / sec
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
SQL Server Management Studio Reports
SQL Server Report Examples
Server-Level Reports Database-Level Reports
Server Dashboard Memory Consumption Activity – All Block
Transactions Activity – Top Sessions Performance – Batch
Execution Statistics Performance – Top Queries
by Average CPU Object Execution Statistics
Disk Usage All Transactions All Blocking Transactions Index Usage Statistics Top Transactions by Age Schema Changes History
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
Monitoring SQL Server Logs
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
Using Dynamic Management Views (DMVs)
DMV Examples
• sys.dm_exec_requests
Query Execution / Processes
• sys.DM_DB_File_Space_Usage
Storage Engine
• sys.DM_DB_Index_Operational_Stats• sys.DM_DB_Index_Physical_Stats
Indexes
• sys.DM_IO_Pending_IO_Requests• sys.DM_IO_Virtual_File_Stats
Disk I/O
• Schema information | Common Language Runtime (CLR)• Database Mirror / Clustering | Replication
Other Categories
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
Using SQLDiag
Using SQL ProfilerMonitoring 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)
Understanding SQL Profiler
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
SQL Server Profiler Architecture
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SQL Profiler Terminology Trace
◦ 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 File◦ Trace data that is saved to a binary file◦ Default extension is “.trc”
Trace Table◦ 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 Trace Template
◦ 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”
Groupings:◦ Event Categories ◦ Event Classes◦ Events
Examples:◦ TSQL◦ Stored Procedures◦ Performance◦ Errors and Warnings◦ Security auditing
Configuring Trace Events
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
Configuring Trace Columns
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)
Trace Output Options
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
Demo: Creating Profiler Traces
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
Other SQL Profiler Options
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
Using System Monitor with SQL Profiler
Using the Database Engine Tuning Advisor
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
Database Engine Tuning Advisor
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
Workload Sources
Limit tuning time Tuning Options◦ Allowed Physical Design Structures (PDS)◦ Keep all/specific existing objects◦Maximum storage space◦Online or offline recommendations◦ Partitioning
DTA Execution Options
Reports can be exported to XML files
Report Examples:
DTA Reports
Workload analysis Column access Table access View-Table
Relations
Statement cost Event frequencyIndex 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
Using the Database Engine Tuning Advisor
Application Design TipsPractical ways to improve database application performance
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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
Application Design Tips
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.)
Application Design Tips (cont’d.)
Managing Processes, Locking, and Deadlocks
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
Understanding Processes
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
Monitoring Processes
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)
Managing Processes
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
Understanding Locking
Blocking◦When transaction(s) must wait for a lock on a resource◦ LOCK_TIMEOUT setting (default = wait forever)
Locking Models:◦ Pessimistic◦Optimistic
Understanding Blocking
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
Transaction Isolation Levels
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
Monitoring Locking Activity
Deadlocks:◦ Two or more tasks permanently block each other based on
resource locks◦Default resolution is within 5 seconds
Deadlock victim ◦ Transaction is rolled-back◦ Process receives a 1205 error
Example:◦ 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
Understanding the Deadlock Process
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
Avoiding Deadlocks
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
Deadlock Victims
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)
Monitoring Deadlocks
Deadlock Graph
Questions & DiscussionFor more information:http://AnilDesai.net [email protected]
