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Oracle: Temporary segment

Temporary segments are needed for operations involving

sorts
hashing
bitmap merging

Temporary segments are also used/created by the following SQL statements

create table as select
alter index rebuild
create index
drop table / drop object (which converts the segment into a temporary segment which is then cleaned up later(?) by SMON?)
create snapshot
create partition table

SMON cleans temporary segments up:

in temporary tablespaces when the database is started up
in permanent tablespaces when the user process has died before it can clean up the segment.

See also

Temporary tablespaces

The following command drops the temporary segments in the tablespace whose id/number is n-1 (MOS Note 1495163.1):

alter session set events 'immediate trace name drop_segments level n`