Database tuning solution

Factors affecting system performance

There are many factors that affect system performance , In order to better analyze these factors that affect the system performance , These factors can be divided into 6 Categories: ：
Server hardware class
Operating system class
Network class
SQL Server System class
Database application class
Customer application class

Strategies for performance monitoring and tuning

Monitoring and adjusting system performance is a comprehensive problem , There is no fixed pattern . however , It is necessary to understand and master the framework steps of monitoring and adjusting the system .
The framework steps of monitoring and adjusting the system are as follows ：
Develop strategies for monitoring and adjusting the system
Choose a scheme to adjust performance
Develop specific methods for performance monitoring and tuning
Establish the performance baseline of the system
Detect performance bottlenecks
Understand common monitoring tasks

SQL Server Profiler

SQL Server Profiler Tools can be used to track various activities of servers and databases . These activities can be captured in the table 、 File or a script file , For later analysis .
Use SQL Server Profiler The process of the tool includes creating a trace 、 Run and reproduce tracking, etc .

Common monitoring and adjustment tasks

Common monitoring and adjustment tasks include monitoring memory usage 、 Monitor thread and processor usage 、 Monitor the input of the hard disk / Output 、 Monitor lock information and query statements with poor performance . Commonly used counters for monitoring system performance .

Methodology of performance tuning

How to design a good relational database architecture

Judgment of data hot area

Define the index according to the data hot area 、 Table split definition

Optimize SELECT Inquire about

Try to store data in the same table
Use index and index coverage policy

Optimize UPDATE Business

Try to put the data that needs to be updated in a smaller table

Optimize DELETE Business

Evaluate the effect of partitions in large-scale deletion

Optimize INSERT Business

Reduce dependence on automatic numbering

Use valid query parameters

SARGs（ Valid format of query parameters ）
Limit to full compliance 、 A range of values 、 Or with AND Connect more than two items to define the search .
Format
Data field Partial operators < Constant or variable >
< Constant or variable > Partial operators Data field
accord with SARGs Example of
FirstName=‘ king ’
6000060000

Easy mistakes

Operate on data fields
Select * from Employees where　LastName+’,’+FirstName=‘Davolio,Nancy
Make a negative query
Not、Exists、Not IN、Not Like、!= <> !> !< etc.
stay where Use functions for data fields in statements
Select * from [order details] where ABS(quantity-100)<1
Use OR Operator
Use OR Do operators , You need all fields to have available indexes

Query optimization

Use T-SQL Precautions for

Select grammar
Try not to return all fields in the data table without configuring filter conditions
If composite index is used , Then the first field in the index order is suitable for filtering
Distinct,Order by Wait for the syntax to be used when the query results are needed
Union All than Union good
If the connection transaction level is not reduced to Read Uncommited, Or through the lock prompt NOLOCK To reduce the chance of congestion , Best configuration SET LOCK_TIMEOUT Options , Avoid users' endless waiting
Insert、Delete and Update
When a large number of batch data operations , nothing Log The behavior must be better than writing data twice （ First record Log Write the database again ） fast .
stay Update and Delete use Where When clause , Remember to meet the conditions SARGs Format

Query tuning options

Use OPTION Clause call table prompt or view prompt
OPTION (TABLE OPTION(dbo.Orders, IDNEX(IX_OrderID)))
FORCESEEK Tips
FROM Orders WITH (FORCESEEK)
OPTION (TABLE HINT(dbo.Orders, IDNEX(0), FORCESEEK))
sys.fn_validate_plan_guide Function is used to verify the effectiveness of the mandatory plan
Program guide support XML ShowPlan Parameters
A new event class is designed for monitoring mandatory plans (Plan Guide Successful and Plan Guide Unsuccessful) And performance counters (SQL Server SQL Statistics Under the object Guided Plan Executions/sec The counter and Misguided Plan Executions/sec Counter )
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