Oracle 11g - Decreasing Big Table Size

I want to reduce the size of a table. > I thought if I could do this with export / import, but when I check it > with the ESTIMATE_ONLY option, it doesn't seem to work. > > I have no chance of using partitioning. > > If I do it with CTAS (create table as select), the archive production > will peak and the disaster database will be affected. > > How can I reduce the size of this table? If I do shrink, will UNDO be > enough and how much space will be enough to add UNDO tablespace to > overcome this problem? Do you have an estimate of how long it will > take if I shrink? > > I have to be very careful as it will be done directly in the > production database. > Version: Oracle 11g Release 2 - Standard Edition > > ASM option: yes > > Cluster: yes > > Partitioning option: no > > Compress data pump option: no Table size information: SQL> select segment_name,sum(bytes)/1024/1024/1024 GB from dba_segments where owner='OWNER_NAME' and segment_type='TABLE' and segment_name=upper('TABLE_NAME') group by segment_name; SEGMENT_NAME GB --------------------------------------------------------------------------------- ---------- TABLE_NAME 392.493164 Export information (It does not work in reducing the table size. ): nohup expdp "'/ as sysdba'" directory=DP_DIR tables=OWNER_NAME.TABLE_NAME ESTIMATE_ONLY=Y & Output: Starting "SYS"."SYS_EXPORT_TABLE_01": "/******** AS SYSDBA" directory=DP_DIR tables=OWNER_NAME.TABLE_NAME ESTIMATE_ONLY=Y Estimate in progress using BLOCKS method... Processing object type TABLE_EXPORT/TABLE/TABLE_DATA . estimated "OWNER_NAME"."TABLE_NAME" 392.4 GB Total estimation using BLOCKS method: 392.4 GB Best regards,