Truncate table will delete the corresponding LOB segment of table or not ?

Question

Hi All,
I have few table with LOB segments, if i fire the truncate table on those table will it purge the LOB segment as well ?
Approximately how much time will take to truncate 100gb LOB segments.
Thanks

Answer 1

903787 wrote:
Hi ,
1.Truncate will delete the LOB segment or not ?It won't delete the LOB segments but it should release most of the allocated space.
>
2.To reclaim space we need to run the below command, is it correct ?
ALTER TABLE <table_name> MODIFY LOB (LOB_COLUMN) (SHRINK SPACE);
Should not be needed in 11.2:
SQL> select * from v$version;
BANNER
Oracle Database 11g Express Edition Release 11.2.0.2.0 - Production
PL/SQL Release 11.2.0.2.0 - Production
CORE    11.2.0.2.0      Production
TNS for 32-bit Windows: Version 11.2.0.2.0 - Production
NLSRTL Version 11.2.0.2.0 - Production
SQL> select count(*) from user_segments;
  COUNT(*)
         0
SQL>
SQL> create table t(x clob);
Table created.
SQL> select segment_name, segment_type, bytes
  2  from user_segments;
SEGMENT_NAME                             SEGMENT_TYPE            BYTES
T                                        TABLE                   65536
SYS_IL0000030908C00001$$                 LOBINDEX                65536
SYS_LOB0000030908C00001$$                LOBSEGMENT              65536
SQL>
SQL> insert into t select lpad(segment_name,8192) from dba_segments;
6312 rows created.
SQL> commit;
Commit complete.
SQL>
SQL> select segment_name, segment_type, bytes
  2  from user_segments;
SEGMENT_NAME                             SEGMENT_TYPE            BYTES
T                                        TABLE                  393216
SYS_IL0000030908C00001$$                 LOBINDEX                65536
SYS_LOB0000030908C00001$$                LOBSEGMENT           53477376
SQL>
SQL> truncate table t;
Table truncated.
SQL>
SQL> select segment_name, segment_type, bytes
  2  from user_segments;
SEGMENT_NAME                             SEGMENT_TYPE            BYTES
T                                        TABLE                   65536
SYS_IL0000030908C00001$$                 LOBINDEX                65536
SYS_LOB0000030908C00001$$                LOBSEGMENT              65536
SQL>
SQL> alter table t modify lob(x) (shrink space);
Table altered.
SQL>
SQL> select segment_name, segment_type, bytes
  2  from user_segments;
SEGMENT_NAME                             SEGMENT_TYPE            BYTES
T                                        TABLE                   65536
SYS_IL0000030908C00001$$                 LOBINDEX                65536
SYS_LOB0000030908C00001$$                LOBSEGMENT              65536
SQL>