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Oracle Database 11gR2 Performance Tuning Cookbook by Ciro Fiorillo

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Using hash clusters

In the previous recipe, we introduced index clusters and tested a particular way to load data in a cluster to optimize the storage of rows with the same cluster key value.

In this recipe, we introduce a different kind of cluster—hash clusters. The biggest difference between index clusters and hash clusters is in the way data is accessed given a particular cluster key value.

How to do it...

The following steps will demonstrate the use of hash clusters:

  1. Connect to the HR schema of the TESTDB database:
    CONNECT hr@TESTDB/hr
    
  2. Create the cluster:
    CREATE CLUSTER EMP_DEPT_CLUSTER (deptid NUMBER(4))
    SIZE 8192 HASHKEYS 100;
    
  3. Create the first table and populate it with data:
    CREATE TABLE CL_DEPARTMENTS CLUSTER EMP_DEPT_CLUSTER (department_id) ...

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