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  • Slide 1
  • SQL Server Optimization for Developers ANIL DESAI ([email protected] | HTTP://ANILDESAI.NET)[email protected]://ANILDESAI.NET AUSTIN.NET USERS GROUP, 04/14/2014
  • Slide 2
  • Presentation Overview Database Performance Goals and Challenges Monitoring and Optimizing Performance Understanding indexes SQL Profiler and Database Engine Tuning Advisor Tuning Database Queries Understanding the Query Optimizer and Execution Plans Seeing the effects of indexes Application Design Best Practices
  • Slide 3
  • Presentation and Demo Notes For Developers, not database administrators No focus on backups, fault-tolerance, data protection, replication, security, etc. Demo Script Run SQL Load Simulator with various queries (need to write queries) Build WAIT FOR statements into the script Disable indexes on Demo schema tables? Use Profiler to capture trace data Use Database Tuning Advisor to test workloads
  • Slide 4
  • Best Practices: Optimize for real-world workloads Monitor/review performance regularly Focus on specific issues Performance Monitoring Process Establish a baseline Identify bottlenecks Make one change at a time Measure performance Repeat (if desired)
  • Slide 5
  • Monitoring and Troubleshooting Scenarios Server-Level Issues Users are reporting slow performance 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
  • Slide 6
  • Which queries are taking the longest to run? Which queries are using the most system resources? Why does database/web site access slow down during particular times or during certain patterns of activity? Is indexing configured optimally for my live (production) database workloads? How will my development updates affect production performance? Which are the most cost-effective upgrades I can make to improve performance? How can I optimize a specific query? Common Datbaase Questions
  • Slide 7
  • SQL Server Editions SQL Server Compact Works with mobile devices (small footprint) Fewer features vs. full SQL Server SQL LocalDB Creates a "user instance" of SQL Server (no installation or services) Supports AttachDbFileName option More functionality vs. SQL Server Compact SQL Server Express Free version of SQL Server (up to 10GB database) SQL Server Standard, Enterprise, Business Intelligence, Developer
  • Slide 8
  • Database Performance Tools System/OS Performance Monitor Resource MonitorTask Manager SQL Server SQL Server Management Studio SQL Profiler / SQL Trace Database Engine Tuning Advisor Dynamic Management Views (DMVs) Query- Level Database Engine Tuning Advisor Query Execution Plans
  • Slide 9
  • 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 9 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
  • Slide 10
  • Database File Structure SQL Server database file structure: Primary data file (.mdf) Secondary data files (*.ndf) Transaction log files (*.ldf) File groups Moving database files: Attaching and detaching databases Storage Goals: Reduce disk contention Optimize read/write performance
  • Slide 11
  • Database Design Issues Transaction processing (OLTP) Favors normalized schema Many tables, each with fewer columns Optimized for write (transactional) activity Reporting and Analysis Centralized, consistent storage of required data Favored by denormalized schema Fewer tables with many columns in each Data is aggregated from multiple sources into a data mart or data warehouse May store aggregates in warehouse
  • Slide 12
  • Understanding Indexes Index types Clustered Index Non-Clustered Indexes Columnstore indexes Indexing strategies Goal is ideal index coverage Index maintenance can slow-down write operations (Insert, Update, Delete) Referential Integrity Primary Key (default = clustered index) Foreign Key references Constraints Statistics (manual vs. automatic)
  • Slide 13
  • General Index Tuning Best Practices Make tuning a part of your development process Dev: Use synthetic workloads and test cases Test: Use real-world databases, whenever possible Production: Capture real usage statistics for analysis Collect a representative workload, whenever possible Consider all applications and workloads when tuning a database Use naming conventions for indexes and related objects Use query hints sparingly (NOLOCK)
  • Slide 14
  • 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) Using SQL Profiler
  • Slide 15
  • Database Engine Tuning Advisor Automatic workload analysis for Physical Design Structures (PDS) Data Source: File (Profiler Trace or.SQL files) Table Plan Cache Tuning Options Keep existing PDS Advanced Features: Partitioning, indexed views, etc.
  • Slide 16
  • Demo: Optimizing Indexes Generate sample queries / tables View query execution plans View the effects of indexes on common queries Capture Performance Data with SQL Profiler SQL Profiler traces, events, and filters Using SQL Load Generator to generate database load Capturing and storing Analyzing and optimizing with Database Tuning Advisor Analyzing index usage reports Saving and applying index recommendations
  • Slide 17
  • Tuning Individual Queries Query Analyzer Features Execution Plan (estimated and actual) Include Client Statistics (multiple trials) Analyze in Database Engine Tuning Advisor (single query) Trace query in SQL Profiler (single query) Keep query logic close to the database Filter returned data at the database layer Minimize the size of result sets Minimize round-trips to the server Use standard (inner) joins, where possible Consider strategic denormalization for core sets of data
  • Slide 18
  • Query Optimizer Details Goal: Find the most efficient method to return the data Come up with a plan quickly Minimize CPU, memory, and I/O requirements Use statistics and index details to improve plans Query plan caching Relational engine vs. storage engine Execution Plan output Save as.sqlplan file for later analysis Output in graphical, text, and XML formats Can store and export plans using SQL Profiler (ShowPlan XML event) Can use query hintsquery hints
  • Slide 19
  • Understanding Execution Plans Optimizing individual queries Rewrite query logic Use other objects (views, stored, procedures, etc.) Strategic demoralization Data Retrieval: Table scan, index seek/scan Index Usage Covering indexes Join conditions
  • Slide 20
  • Execution Plan Example
  • Slide 21
  • Execution Plans in Windows Azure
  • Slide 22
  • Client Statistics Example
  • Slide 23
  • Demo: Tuning Queries Viewing the effects of indexes on specific queries
  • Slide 24
  • Application Design Best Practices Create an abstraction layer between business and database objects ADO.NET Microsoft Enterprise Library Microsoft Enterprise Library NHibernate Entity Framework Use caching wherever possible Server-side (web services) Application-level (middle tier) Client-side (desktop or mobile apps) Minimize transaction times
  • Slide 25
  • Dev Best Practices: Application and Data Architecture Standards-based communications Loosely-coupled tiers and components Architecture Test harness Unit tests that use data Query performance monitoring Development / Testing Windows PerfMon Counters Instrumentation and Logging Alerts / pro-active corrections Auto-scaling Performance and Monitoring Error and event handling Transaction retry (random interval); Deadlock management User notifications (responsive UI / cancel and retry options) Reliability
  • Slide 26
  • Windows Azure and Cloud Databases Practical cloud benefits Data redundancy and geographic distribution Lower management overhead Potential issues Keeping data close to applications and services Data synchronization Network performance issues Data security, legal issues, and regulatory compliance Determine where/how to use cloud-based services SaaS vs. PaaS vs. IaaS
  • Slide 27
  • Azure Database Services SQL Azure Database Cost-effective, managed database instances Can be managed with standard tools (Visual Studio and SSMS) Some limitations (CLR, Mirroring, Partitioning, Replication, Extended SPs) Other Services Azure Virtual Machines (SQL Server templates) Azure Web Sites (with gallery templates) A