Is it safe to delete dumthe tables Oracle 11g XE

Because of deferred segment creation.

In Oracle 11.2, when you create a table with no data, you no longer allocate any space in the tablespace. Oracle doesn't actually create the segment until you try to insert data into the table. This is a difference from earlier versions in which the segment was created when the table was created rather than when data was inserted.

The reason for the new feature is that there are a lot of packaged applications on the market that create potentially hundreds of tables that will never have data because the customer isn't using some specific module of the project that uses those tables. It was annoying for someone that packaged a big ERP tool, for example, to end up with potentially GB of space allocated to tables that would never have any data.

You'll only see deferred segment creation if you've set COMPATIBLE to 11.2 and if DEFERRED_SEGMENT_CREATION is set to the default of TRUE

SQL> conn / as sysdba
Connected.
SQL> show parameter compatible

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
compatible                           string      11.2.0.0.0
SQL> show parameter deferred

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
deferred_segment_creation            boolean     TRUE
SQL> create user deferred identified by deferred default tablespace users;

User created.

SQL> crant create table, create session to deferred;
SP2-0734: unknown command beginning "crant crea..." - rest of line ignored.
SQL> grant create table, create session to deferred;

Grant succeeded.

SQL> conn deferred/deferred
Connected.
SQL> create table test( col1 number );

Table created.

SQL> insert into test values( 1 );
insert into test values( 1 )
            *
ERROR at line 1:
ORA-01950: no privileges on tablespace 'USERS'

Metalink 207303.1 is the Client/ Server Interoperability Matrix which will be the definitive documentation. Since the express edition of 10g is based on Oracle 10.2, a database link to an 8.1.7 database should be supported. Database links to earlier versions of 8i (8.1.5 or 8.1.6) are not supported from a 10.2 database. For general sanity, I'd strongly suggest that the 8i side be running at least the 8.1.7.4 patchset but that isn't strictly required.