To determine the on disk size of Analytic Workspace segments in tablespaces consider using this script. This is especially important in 11g when used with LOB COMPRESSION or Secure LOBs. It will give you the most accurate "On Disk" size for your object.

set pages 500 lines 110

bre on REPORT;
comp sum lab "Total Disk:" of mb on REPORT;
col awname format a35 heading "Analytic Workspace (Partitions)"
col tablespace_name format a18 heading "Tablespace"
col logging format a8 heading "Logging"
col mb format 999,999,990.00 heading "On Disk MB"

select dl.owner||'.'||substr(dl.table_name,4)||' ('||count(ds.segment_name)||')' awname,
sum(ds.bytes)/1024/1024 as mb, ds.tablespace_name, logging
from dba_lobs dl, dba_segments ds
where dl.column_name = 'AWLOB' and dl.segment_name = ds.segment_name
group by dl.owner, dl.table_name, ds.tablespace_name, logging order by dl.owner, dl.table_name;

Analytic Workspace (Partitions)..........On Disk MB Tablespace.........Logging
----------------------------------- --------------- ------------------ --------
SCOTT1.EXAMPLE1 (16).......................6,960.00 USERS..............NONE
SCOTT2.AW_TST (16)............................27.50 USERS..............NONE
SCOTT3.EXAMPLE1 (16)..........................10.56 USERS..............NONE
SCOTT4.TEST (16)...........................6,936.00 USERS..............NONE
SCOTT5.EXAMPLE0 (16)..........................99.00 USERS..............NONE
SCOTT6.EXAMPLE (16)........................7,022.00 USERS..............NONE
SCOTT7.TEST (16)..............................28.50 USERS..............NONE
SYS.AWCREATE (1)...............................3.00 SYSAUX.............YES
SYS.AWCREATE10G (1)............................0.81 SYSAUX.............YES
SYS.AWMD (1)...................................7.00 SYSAUX.............YES
SYS.AWREPORT (1)...............................0.81 SYSAUX.............YES
SYS.AWXML (1).................................10.00 SYSAUX.............YES
SYS.EXPRESS (1)................................2.00 SYSAUX.............YES
....................................---------------
Total Disk:...............................21,187.37