1、What Does the DBA Tune?
Performance tuning areas
- Application:(Shared with developers)
- SQL statement performance
- Change management
- Instance tuning:
- Mermory
- Database structure
- Instance configuration
- Operating system interactions:(Shared with SA)
- I/O
- Swap
- Parameters
2、Tuning Questions
- Who tunes?
- Application designers
- Application developers
- Database administroators
- System adminstrators
- What to tune?
- How much tuning is required?
- Response Time
-
- inreaseing throughput 吞吐量高（尽可能减少Oracle对磁盘的操作，尽可能在内存中读写数据）
- 提高缓存的命中率
3、Tuning Phases
SLA（Servie Level Agreement）
调优的时候，定义个量化的东西；按照这个量化的东西来展开调优；
Tuning can be divided into different phases:
- Application design and programming
- Database configuration
- Adding a new application to an existing database
- Troubleshooting and tuning
4、Common Performance Problems
Bad session management:
Limits saclability to point that cannot be exceeded
Makes the system one or two orders of magnitude slower than it should be
Bad cursor management:
Bad relational design:
Unnecessary table joins performed
Usually a result of trying to build an object interface to relational storage
5、Tuning Steps In Development
Tune the design
Tune the apppliation
Tune the memory
Tune I/O
Tune connection
Tune the operating system
6、Baseline of Statistics
A baseline set of statistics is used to
Provide a set of statistics that are collected when the system was operating within the bounds set
Create a hypothesis about what has changed on the system
7、Steps for a Production DB
Define the problem
- Examine the host system and Oracle statistics
- Consider some common performance errors
- Build a conceptual mode
- Implement and measure the change
- Check that the bottleneck has been resolved
8、Tuning Methodology
- Check alert log and trace files for errors
- Chekc the parameter file for any diagnostic or inappropriate parameter setting.
- Check memory,I/O,and CPU usage.Indentify processes with resource usage anomalies.
- Identify and tune SQL statements that are heavy consumers of CPU or I/O.
- Tuning response time:
- Analyze system performance in terms of work done(CPU or service time)versus time spent waiting for work(wait time)
- Determine which component consumes the greatest amount of time.
- Drill down to tune taht component ,if appropriate.
9、Trade-Offs of Performance & Safty
Factors that affect performances
- Multiple control files
- Multiple redo log members in a group
- Frequnet checkpointing
- Backing up data files
- Performing archiving
- Block check numbers
- Number of concurrent users and transactions
10、Summary
In this lesson,you should have learned how to:
- Create a good inital design
- Define a tuning methodology
- Perform production tuning
- Establish quantifiable goals
- List tuning problems
- Decide between performance and safety