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Specifying the Percent of Index Page Space for Expansion

When you define an index, specify an appropriate FILLFACTOR for the amount of expansion you expect. When the index is created, the database server fills each page only to the percent of fullness that you specify.

For indexes on stable or STATIC tables, specify a high FILLFACTOR for faster selects. For indexes on tables that grow rapidly, specify a low FILLFACTOR for efficient updates.

With the default FILLFACTOR of 90, ninety percent of each index page is filled initially. As index entries are added or removed, the number of index keys on each page changes. If the size of the indexed table increases, the size of the index also increases, and the unused space in index pages is filled. When the entire page is filled, the next index entry requires the database server to split index nodes and create new branches. This activity slows transaction processing and makes the index less efficient.

For information about index structure, refer to the IBM Informix: Extended Parallel Server Administrator's Reference.

The FILLFACTOR configuration parameter specifies the default value for all indexes. Adjust this parameter to specify an appropriate value for most indexes in your database, and specify a different value for indexes, as appropriate. This parameter can be modified with the server on-line using the onutil SET command.

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