The objective of tuning a system is either to reduce the response time for end users of the system, or to reduce the resources used to process the same work.

The objective of tuning a system is either to reduce the response time for end users of the system, or to reduce the resources used to process the same work. You can accomplish both of these objectives in several ways:

• Reduce the Workload
• Balance the Workload
• Parallelize the Workload

Reduce the Workload

This is what commonly constitutes SQL tuning: finding more efficient ways to process the same workload. It is possible to change the execution plan of the statement without altering the functionality to reduce the resource consumption.

Two examples of how resource usage can be reduced are:

1. If a commonly executed query needs to access a small percentage of data in the table, then it can be executed more efficiently by using an index. By creating such an index, you reduce the amount of resources used.
2. If a user is looking at the first twenty rows of the 10,000 rows returned in a specific sort order, and if the query (and sort order) can be satisfied by an index, then the user does not need to access and sort the 10,000 rows to see the first 20 rows.

Balance the Workload

Systems often tend to have peak usage in the daytime when real users are connected to the system, and low usage in the nighttime. If noncritical reports and batch jobs can be scheduled to run in the nighttime and their concurrency during day time reduced, then it frees up resources for the more critical programs in the day.

Parallelize the Workload

Queries that access large amounts of data (typical data warehouse queries) often can be parallelized. This is extremely useful for reducing the response time in low concurrency data warehouse. However, for OLTP environments, which tend to be high concurrency, this can adversely impact other users by increasing the overall resource usage of the program.