Will DDL statement commit automatically

I have read in some books that issuing ddl statement will commit the transaction automatically irrespective of the success of the DDL statement.

I performed a small test and came to a conclusion that,

• If ddl statement is executed successfully, the transaction is committed automatically.
• If ddl statement fails due to logical error, the transaction is committed automatically.
• If ddl statement fails due to syntax error, the transaction is neither committed nor rolled back, the transaction is still open.

Details of the test performed

SQL> create table testddl ( a number, b date);
Table created.
SQL> insert into testddl values (1, sysdate);
1 row created.
SQL> insert into testddl values (2, sysdate);
1 row created.
Not committed.
SQL> alter table testddl add constraint a_uq unique (a);
Table altered.
Automatically commits - ddl statement succeed.

SQL> rollback;
Rollback complete.

SQL> select * from testddl;
A B
-- --------
1 10-SEP-08
2 10-SEP-08

SQL> insert into testddl values (3, sysdate);
1 row created.
SQL> insert into testddl values (4, sysdate);
1 row created.
not committed

SQL> alter table testddl add constraint b_fk b references test (b);
alter table testddl add constraint b_fk b references test (b)
*
ERROR at line 1:ORA-01430: column being added already exists in table

Error but automatically commits. DDL Failed due to logical error.

SQL> rollback;
Rollback complete.

SQL> select * from testddl;
A B
-- --------
1 10-SEP-08
2 10-SEP-08
3 10-SEP-08
4 10-SEP-08

SQL> insert into testddl values (5, sysdate);
1 row created.
SQL> insert into testddl values (6, sysdate);
1 row created.
not committed

SQL> alter table testddl drp constraint a_uq;
alter table testddl drp constraint a_uq
*
ERROR at line 1:ORA-01735: invalid ALTER TABLE option

Error. ddl failed due to syntax error.Will not commit automatically.

SQL> rollback;
Rollback complete.

SQL> select * from testddl;
A B
-- --------
1 10-SEP-08
2 10-SEP-08
3 10-SEP-08
4 10-SEP-08

This is how the ddl statement is processed.
DDL parse
If success
commit
execute ddl
commit
end if
else
do nothing.

Hope you have enjoyed...