ORA-20000

Here's a simple request. The request takes into account the size of the table, including indexes, lobs and nested tables.

select '&TABLE' as table_name, sum(dba_segments.BYTES) / 1024 / 1024 as Mb
from   dba_segments
where  (dba_segments.owner, dba_segments.segment_name) in
       (
         -- table
         select '&OWNER' as owner,
                '&TABLE' as segment_name
         from   dual
         union all
         -- lob segments
         select dba_lobs.owner, dba_lobs.segment_name
         from   dba_lobs
         where  dba_lobs.owner = '&OWNER' and
                dba_lobs.table_name = '&TABLE'
         union all
         -- lob index segments
         select dba_lobs.owner, dba_lobs.index_name
         from   dba_lobs
         where  dba_lobs.owner = '&OWNER' and
                dba_lobs.table_name = '&TABLE'
         union all
         -- nested tables
         select dba_nested_tables.owner, dba_nested_tables.table_name
         from   dba_nested_tables
         start with dba_nested_tables.owner = '&OWNER' and
                    dba_nested_tables.parent_table_name = '&TABLE'
         connect by dba_nested_tables.parent_table_name = prior dba_nested_tables.table_name
         union all
         -- indexes
         select dba_indexes.owner, dba_indexes.index_name
         from   dba_indexes
         where  dba_indexes.table_owner = '&OWNER' and
                dba_indexes.table_name = '&TABLE'
       )