One of the fastest ways to achieve good Oracle performance tuning results is to utilize SQL Optimization on individual SQL statements.
Successful Oracle Performance Tuning with SQL Optimization
Proper tuning of SQL statements is the key to SQL optimization Visit the Oracle library cache to determine which SQL statements you may want to optimize. Extract the statements and order them depending on the amount of execution activity. You can then begin the SQL optimization process:
- Locate High-Impact SQL Statements
Rank the extracted SQL statement according to their number of executions. You should tune each statement by their ranking beginning with the ones with the most executions. You can realize a great deal of performance improvement by concentrating on these most frequently executed statements.
- Obtain the Execution Plan for the SQL Statements
Using either Oracle’s explain utility or another third-party tool, you will need to determine the execution plan of the SQL statements. The execution paths of the statements will be run without the necessity of executing the SQL statements. You can then output their execution plan to a plan table. Here you will be able to determine which statements have sub-optimal execution plans and need to be optimized.
- Tuning the Statements
Now that you’ve determined which statements must be tuned, you can tune the individual statements for better performance. The best way to tune the individual statements is rewrite them for efficient SQL usage.
Tips for More Efficient SQL
While there many details involved in Oracle Performance Tuning, most of the rules for writing efficient SQL aren’t that complicated. They are basic rules that, when followed precisely, can produce a great return on SQL writing efforts. Follow these guidelines for success:
- Rewrite complex subqueries with temporary tables
- Replace EXISTS subqueries with minus subqueries
- Use decode and case function to reduce the number of times a table must be selected
- Utilize table aliases when referencing columns within tables
- It may be counter-intuitive, but full-table scans are sometimes faster than index scans
- Always have a matching function-based index when using a calculation on an indexed column
Follow these and other rules for SQL writing to achieve successful results for SQL optimization with your Oracle performance tuning efforts.
