The tablespace map in Space Manager version 7.0 installed on an Oracle 10g database is very slow.
Data dictionary tables statistics is not updated/analyzed.
Oracle's recommendation for 10g is to keep the data dictionary tables statstics updated. Space Manager is querying SYS views when loading tablespace map and other components. Refer to Oracle documentation on how to update dictionary statistics.
To confirm if the dictionary statistics are not updated, run the following:
select count (*) as dd_tables_not_analyzed from dba_tables where owner = 'SYS' and last_analyzed is null ;
select min (last_analyzed), max (last_analyzed) from dba_tables where owner = 'SYS' and last_analyzed is not null ;