A cluster can be dropped if the tables within the cluster are no longer needed. When a cluster is dropped, so are the tables within the cluster and the corresponding cluster index. All extents belonging to both the cluster data segment and the index segment of the cluster index are returned to the containing tablespace and become available for other segments within the tablespace.
To drop a cluster that contains no tables, and its cluster index, use the DROP CLUSTER statement. For example, the following statement drops the empty cluster named emp _dept:DROP CLUSTER emp_dept;
If the cluster contains one or more clustered tables and you intend to drop the tables as well, add the INCLUDING TABLES clause of the DROP CLUSTER statement, as follows:DROP CLUSTER emp_dept INCLUDING TABLES;
If the INCLUDING TABLES clause is not included and the cluster contains tables, an error is returned.
If one or more tables in a cluster contain primary or unique keys that are referenced by FOREIGN KEY constraints of tables outside the cluster, the cluster cannot be dropped unless the dependent FOREIGN KEY constraints are also dropped. This can be easily done using the CASCADE CONSTRAINTS clause of the DROP CLUSTER statement, as shown in the following example:DROP CLUSTER emp _dept INCLUDING TABLES CASCADE CONSTRAINTS;
The database returns an error if you do not use the CASCADE CONSTRAINTS clause and constraints exist.
Dropping Clustered Tables
To drop a cluster, your schema must contain the cluster or you must have the DROP ANY CLUSTER system privilege. You do not need additional privileges to drop a cluster that contains tables, even if the clustered tables are not owned by the owner of the cluster.
Clustered tables can be dropped individually without affecting the cluster, other clustered tables, or the cluster index. A clustered table is dropped just as a nonclustered table is dropped, with the DROP TABLE statement.
Dropping Cluster Indexes
A cluster index can be dropped without affecting the cluster or its clustered tables. However, clustered tables cannot be used if there is no cluster index; you must re -create the cluster index to allow access to the cluster. Cluster indexes are sometimes dropped as part of the procedure to rebuild a fragmented cluster index.
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Oracle 10g Tutorial
Overview Of Administering An Oracle Database
Creating An Oracle Database
Starting Up And Shutting Down
Managing Oracle Database Processes
Managing Control Files
Managing The Redo Log
Managing Archived Redo Logs
Managing Datafiles And Tempfiles
Managing The Undo Tablespace
Using Oracle-managed Files
Using Automatic Storage Management
Managing Space For Schema Objects
Managing Partitioned Tables And Indexes
Managing Hash Clusters
Managing Views, Sequences, And Synonyms
General Management Of Schema Objects
Detecting And Repairing Data Block Corruption
Managing Users And Securing The Database
Managing Automatic System Tasks Using The Maintenance Window
Using The Database Resource Manager
Moving From Dbms_job To Dbms_scheduler
Overview Of Scheduler Concepts
Using The Scheduler
Administering The Scheduler
Distributed Database Concepts
Managing A Distributed Database
Developing Applications For A Distributed Database System
Distributed Transactions Concepts
Managing Distributed Transactions
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