A COMMIT statements after DDL

You don't need to commit before or after you run ddl. Every ddl statements runs as this pseudocode:

BEGIN
   COMMIT;
   YOURE-DDL-OPERATOR;
   COMMIT;
EXCEPTION
   WHEN OTHERS THEN
        ROLLBACK;
        RAISE;
END;

This very simple example can demonstrate you that both commit statements are performed:

SQL> SELECT * FROM D1;

no rows selected

SQL> INSERT INTO D1 VALUES (1);

1 row created.

SQL> ALTER TABLE D1 ADD A NUMBER;
ALTER TABLE D1 ADD A NUMBER
                   *
ERROR at line 1:
ORA-01430: column being added already exists in table


SQL> ROLLBACK;

Rollback complete.

SQL> SELECT * FROM D1;

         A
----------
         1

SQL> INSERT INTO D1 VALUES (2);

1 row created.

SQL> ALTER TABLE D1 ADD B NUMBER;

Table altered.

SQL> ROLLBACK;

Rollback complete.

SQL> SELECT * FROM D1;

         A          B
---------- ----------
         1
         2

SQL>

Rows added and transaction commited whenever DDL operator completed successfully or not.

Also autocommit runs in some tools, did you know that sqlplus do it every time you exit?

SQL> select * from d1;

no rows selected

SQL> insert into d1 values (1);

1 row created.

SQL> select * from d1;

         A
----------
         1

SQL> exit
Disconnected from Oracle Database 10g Express Edition Release 10.2.0.1.0 - Produ
ction

D:\Documents and Settings\501752478>sqlplus hr/hr@xe

SQL*Plus: Release 10.2.0.1.0 - Production on TЄ L¦э 7 13:57:39 2011

Copyright (c) 1982, 2005, Oracle.  All rights reserved.


Connected to:
Oracle Database 10g Express Edition Release 10.2.0.1.0 - Production

SQL> select * from d1;

         A
----------
         1