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Using USE INDEX HINTS and USE ESSENTIAL INDEX HINTS: Criteria for Passing Indexes to the Database

This topic is part of Troubleshooting Siebel EIM Performance. It explains how Siebel EIM determines which indexes to include on the hint clause passed to the database when using the USE INDEX HINTS and USE ESSENTIAL INDEX HINTS parameters.

See also:

• Using the USE INDEX HINTS and USE ESSENTIAL INDEX HINTS Parameters
• Using USE INDEX HINTS and USE ESSENTIAL INDEX HINTS: Example

When determining which indexes to pass on to the database as index hints, Siebel EIM takes the following steps:

1. Before generating a query, Siebel EIM makes a list of columns for which it has determined that an index is needed.
2. Siebel EIM then checks all of the indexes in the repository to find the index with the most matching columns.

Siebel EIM uses the following selection criteria in choosing indexes:

• Unique indexes have priority over nonunique indexes.
• Required columns have priority over nonrequired columns.

If a new index is created and it is declared in the repository, then there is a chance that Siebel EIM will choose it and pass it to the database on a hint.