/* 
	Get extent and max extent information
*/

SELECT
 SubStr(owner || '.' || segment_name, 0, 150) object
 , extents
 , max_extents
FROM dba_segments

/

/* 
	Get extent information for tables close to the max extents 
*/

SELECT
 SubStr(owner || '.' || segment_name, 0, 150) object
 , extents
 , max_extents
FROM dba_segments
WHERE ((max_extents - 100) < extents)

/

/* 
	Alter Extent Size - Table
*/
ALTER TABLE schema.table_name STORAGE ( MAXEXTENTS 20480 )

/

/* 
	Alter Extent Size - Index
*/
ALTER INDEX schema.index_name STORAGE ( MAXEXTENTS 20480 )