Tuning query processing

You can tune a federated system to improve the performance of query processing.

About this task

When you submit SQL queries to the federated database, the SQL compiler processes the query, and the query optimizer analyzes it and creates an access plan. The query optimizer stores the access plan information in the Explain tables in the federated database. You can use the Explain table format and db2expln tool to understand the access plan for a particular SQL statement.

Procedure

To tune federated systems to improve query processing:

Procedure

  1. Submit the SQL queries that you want to tune to the federated database.
  2. Analyze where the query is being evaluated.
  3. Investigate the reasons for the decisions that were made in the access plan and modify your system to increase opportunities for pushdown.