SQL Server 2000 Performance Guidelines

- J.D. Meier, Srinath Vasireddy, Ashish Babbar, Sharon Bjeletich and Alex Mackman

Schema

• Devote the appropriate resources to schema design.
• Separate OLAP and OLTP workloads.
• Normalize first, denormalize for performance later.
• Define all primary keys and foreign key relationships.
• Define all unique constraints and check constraints.
• Choose the most appropriate data type.
• Use indexed views for denormalization.
• Partition tables vertically and horizontally.

Queries

• Know the performance and scalability characteristics of queries.
• Write correctly formed queries.
• Return only the rows and columns needed.
• Avoid expensive operators such as NOT LIKE.
• Avoid explicit or implicit functions in WHERE clauses.
• Use locking and isolation level hints to minimize locking.
• Use stored procedures or parameterized queries.
• Minimize cursor use.
• Avoid long actions in triggers.
• Use temporary tables and table variables appropriately.
• Limit query and index hints use.
• Fully qualify database objects.

Indexes

• Create indexes based on use.
• Keep clustered index keys as small as possible.
• Consider range data for clustered indexes.
• Create an index on all foreign keys.
• Create highly selective indexes.
• Consider a covering index for often-used, high-impact queries.
• Use multiple narrow indexes rather than a few wide indexes.
• Create composite indexes with the most restrictive column first.
• Consider indexes on columns used in WHERE, ORDER BY, GROUP BY, and DISTINCT clauses.
• Remove unused indexes.
• Use the Index Tuning Wizard.

Transactions

• Avoid long-running transactions.
• Avoid transactions that require user input to commit.
• Access heavily used data at the end of the transaction.
• Try to access resources in the same order.
• Use isolation level hints to minimize locking.
• Ensure that explicit transactions commit or roll back.

Stored Procedures

• Use Set NOCOUNT ON in stored procedures.
• Do not use the sp_ prefix for custom stored procedures.

Execution Plans

• Evaluate the query execution plan.
• Avoid table and index scans.
• Evaluate hash joins.
• Evaluate bookmarks.
• Evaluate sorts and filters.
• Compare actual versus estimated rows and executions.

Execution Plan Recompiles

• Use stored procedures or parameterized queries.
• Use sp_executesql for dynamic code.
• Avoid interleaving DDL and DML in stored procedures, including the tempdb database DDL.
• Avoid cursors over temporary tables.

SQL XML

• Avoid OPENXML over large XML documents.
• Avoid large numbers of concurrent OPENXML statements over XML documents.

Tuning

• Use SQL Profiler to identify long-running queries.
• Take note of small queries called often.
• Use sp_lock and sp_who2 to evaluate blocking and locking.
• Evaluate waittype and waittime in master..sysprocesses.
• Use DBCC OPENTRAN to locate long-running transactions.

Testing

• Use tables that contain a realistic amount and distribution of data.
• Ensure that your transaction logs do not fill up.
• Budget your database growth.
• Use tools to populate data.
• Use existing production data.
• Use common user scenarios with a balance between read and write operations.
• Use testing tools to perform stress and load tests on the system.

Monitoring

• Keep statistics up to date.
• Use SQL Profiler to tune long-running queries.
• Use SQL Profiler to monitor table and index scans.
• Use Performance Monitor to monitor high resource usage.
• Set up an operations and development feedback loop.

Deployment Considerations

• Use default server configuration settings for most applications.
• Locate logs and the tempdb database on separate devices from the data.
• Provide separate devices for heavily accessed tables and indexes.
• Use the appropriate RAID configuration.
• Use multiple disk controllers.
• Pre-grow databases and logs to avoid automatic growth and fragmentation performance impact.
• Maximize available memory.
• Manage index fragmentation.
• Keep database administrator tasks in mind.