A zone map is an independent access structure that divides data blocks into zones. Oracle Database implements each zone map as a type of materialized view.

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Whenever CLUSTERING is specified on a table, the database automatically creates a zone map on the specified clustering columns. The zone map correlates minimum and maximum values of columns with consecutive data blocks in the attribute-clustered table. Attribute-clustered tables use zone maps to perform I/O reduction.

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You can create attribute-clustered tables that do not use zone maps. You can also create zone maps without attribute-clustered tables. For example, you can create a zone map on a table whose rows are naturally ordered on a set of columns, such as a stock trade table whose trades are ordered by time. You execute DDL statements to create, drop, and maintain zone maps.

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See also

• “Overview of Materialized Views”
• Oracle Database Data Warehousing Guide to learn more about zone maps

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