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Clusters provide an optional method of storing table data. A cluster comprises of a group of tables that share the same data blocks, and which are grouped together because they share common columns and are often used together. The related columns of tables stored in a cluster are known as the cluster key.

There are two types of clusters:

  • Index
  • Hash

Index clusters store the cluster data together and index the cluster key, which should make them faster at retrieving a range of data rows.

Hash clusters apply hashing functions to the cluster key to determine the physical location of a data row, which should make them faster at retrieving specific data rows.

Note: To place a table on a cluster, 6 include the ON CLUSTER syntax within the CREATE TABLE statement. Placing a table on a cluster precludes you from placing it on a tablespace or defining the associated storage parameters.

Creating and editing

DBMS platform availability and object actions/operations supported

The table below lists the platforms on which this object type is available. It also lists the object actions available against objects of this type For an introduction to object actions and details on usage of specific actions, see Object actions.


Allocate Extent


Deallocate Unused Space