This morning perform a query on the DBA_SEGMENTS, some tablespaces had a segment of type SPACE_HEADER and segment_name a number, as in the example below. In the event that there is this number, this indicates that the tablespace was migrated from ‘dictionary managed’ to ‘locally managed’. This is done with the ‘dbms_space_admin.tablespace_migrate_to_local ()’ package.
The space header segment contains the extent bitmap and is allocated during the migration of the tablespace. Since there is no reserved space. In the case of news tablespaces it is created space for bitmap.
ORA10*ANTO> select segment_name, segment_type from dba_segments where segment_name ='1206.91302' 2 ; SEGMENT_NAME SEGMENT_TYPE _____________________ _____________ ... 1206.91302 SPACE HEADER ...
HTH – Antonio NAVARRO