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Dropping Tablespaces in Oracle

You can drop a tablespace and its contents (the segments contained in the tablespace) from the database if the tablespace and its contents are no longer required.
You must have the DROP TABLESPACE system privilege to drop a tablespace.

Caution:

Once a tablespace has been dropped, the data in the tablespace is not recoverable.
Therefore, make sure that all data contained in a tablespace to be dropped will not be required in the future.
Also, immediately before and after dropping a tablespace from a database, back up the database completely.
This is strongly recommended so that you can recover the database if you mistakenly drop a tablespace, or if the database experiences a problem in the future after the tablespace has been dropped.
When you drop a tablespace, the file pointers in the control file of the associated database are removed.
You can optionally direct Oracle Database to delete the operating system files (datafiles) that constituted the dropped tablespace.
If you do not direct the database to delete the datafiles at the same time that it deletes the tablespace, you must later use the appropriate commands of your operating system to delete them.
You cannot drop a tablespace that contains any active segments. For example, if a table in the tablespace is currently being used or the tablespace contains undo data needed to roll back uncommitted transactions, you cannot drop the tablespace.
The tablespace can be online or offline, but it is best to take the tablespace offline before dropping it.

To drop a tablespace, use the DROP TABLESPACE statement.

The following statement drops the users tablespace, including the segments in the tablespace:

DROP TABLESPACE tablespacename INCLUDING CONTENTS;

If the tablespace is empty (does not contain any tables, views, or other structures), you do not need to specify the INCLUDING CONTENTS clause.

Use the CASCADE CONSTRAINTS clause to drop all referential integrity constraints from tables outside the tablespace that refer to primary and unique keys of tables inside the tablespace.

To delete the datafiles associated with a tablespace at the same time that the tablespace is dropped, use the INCLUDING CONTENTS AND DATAFILES clause.

The following statement drops the users tablespace and its associated datafiles:

DROP TABLESPACE tablespacename INCLUDING CONTENTS AND DATAFILES;

A message is written to the alert log for each datafile that is deleted. If an operating system error prevents the deletion of a file, the DROP TABLESPACE statement still succeeds, but a message describing the error is written to the alert log.

REFERENCE: http://docs.oracle.com/cd/B28359_01/server.111/b28310/tspaces009.htm#ADMIN11383

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