Get started Bring yourself up to speed with our introductory content.

Is your SQL optimized?

To check that your SQL is using the most optimized path, you should run EXPLAIN PLAN against the SQL.

This is a useful tip to help a DBA figure out if certain SQL has been optimized. It gives information in text and graphic form that shows how it's accessing tables and indexes. It also shows all the objects used in the plan and information about those objects such as tablesize, number of records, and more. It has been tested on DB2 UDB v6,7, 8.

Here are the steps to take:

  1. Put the SQL in a CLP file
  2. Run this command:
    db2 connect to <database>
  3. Run this command:
    db2 set current explain mode explain
  4. Run your SQL:
    db2 -vtf   *.CLP
  5. Run this command:
    db2exfmt -d <database> -1 -g TIC -o outputfile
This will put the explain plan in a text file that you can view and check out.

For More Information

  • Feedback: E-mail the editor with your thoughts about this tip.
  • More tips: Hundreds of free DB2 tips and scripts.
  • Tip contest: Have a DB2 tip to offer your fellow DBAs and developers? The best tips submitted will receive a cool prize -- submit your tip today!
  • Ask the Experts: Our SQL, database design, Oracle, SQL Server, DB2, metadata, and data warehousing gurus are waiting to answer your toughest questions.
  • Forums: Ask your technical DB2 questions--or help out your peers by answering them--in our active forums.
  • Best Web Links: DB2 tips, tutorials, and scripts from around the Web.

Dig Deeper on iSeries SQL commands and statements

Start the conversation

Send me notifications when other members comment.

Please create a username to comment.