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Snippet Name: INDEXES: Alter Index Deallocate Unused

Description: Use the deallocate_unused_clause to explicitly deallocate unused space at the end of the index and make the freed space available for other segments in the tablespace. If index is range-partitioned or hash-partitioned, then Oracle Database deallocates unused space from each index partition. If index is a local index on a composite-partitioned table, Oracle Database deallocates unused space from each index subpartition.

Deallocation of space is subject to the following restrictions:

- You cannot specify this clause for an index on a temporary table.

- You cannot specify this clause and also specify the rebuild_clause.

The KEEP clause lets you specify the number of bytes above the high water mark that the index will have after deallocation. If the number of remaining extents is less than MINEXTENTS, then MINEXTENTS is set to the current number of extents. If the initial extent becomes smaller than INITIAL, then INITIAL is set to the value of the current initial extent. If you omit KEEP, all unused space is freed.

Also see:
» INDEXES: View table indexes
» INDEXES: Analyze Index
» INDEXES: Block Dump
» INDEXES: Rebuild Reverse
» INDEXES:
» INDEXES: ENABLE (function-based index)
» INDEXES: DISABLE (function-based index)
» INDEXES: Alter Index Parallel
» INDEXES: Alter Index Allocate Extent
» INDEXES: Virtual / NoSegment
» INDEXES: Reverse Key Indexes
» INDEXES: Bitmap Join Indexes
» INDEXES: Bitmap Indexes
» INDEXES: Unique indexes
» INDEXES: Parallel Index
» INDEXES: Compute Statistics
» INDEXES: SORT and NOSORT
» INDEXES: Function-Based Index
» INDEXES: DROP index
» INDEXES: Alter index
» INDEXES: Single Column Non-unique
» INDEXES: Index Usage Notes
» Compressed Indexes
» Create INDEX

Comment: (none)

Language: PL/SQL
Highlight Mode: PLSQL
Last Modified: March 11th, 2009

-- syntax 
ALTER INDEX <index_name> DEALLOCATE UNUSED;
 
ALTER INDEX <index_name> DEALLOCATE UNUSED
KEEP <integer> <K|M>;
 
 
-- example: 
 
SELECT SUM(bytes), SUM(blocks)
FROM user_extents
WHERE segment_name = 'IDX_SALES_REGION';
 
ALTER INDEX idx_sales_region
DEALLOCATE UNUSED KEEP 512;


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