Effective Tuning Goals

Both tuning goals and SLAs must have three characteristics to be effective. They are:

• Specific
• Measurable 
• Achievable

“Make the instance run as fast as possible” is not specific. A specific goal would be “The month end report suite must complete in less than 4 hours.”

• A goal that is specific is easily made measurable as well. 

The goal of “user response time to a request is 10 seconds” is easily stated, but

• Is this for all user requests? 
• Is it the average response time? 
• How do you measure average response time? 

Having specific definitions for the words of your goal is essential. By restating the goal as “User response time to a particular request is 20 seconds or less,” you can objectively determine when the goal has been met.

• Achievable goals are possible and within the control of the persons responsible for tuning.

The following are examples of unachievable goals for a typical DBA: 

• When the goal is to tune the instance to create a high-performance application, but you are not allowed to change the SQL or the data structures, there is a limited amount of tuning that is possible. 

• When the goal is to have a response time of 1 second, but the network latency between the server and the client is 2 seconds. Without a change to the network, a response time of 1 second is impossible. 

You should always establish measurable tuning goals. Without a tuning goal, it is difficult to determine when you have performed enough tuning.