Teradata session is available in two modes
1) BTET (Begin transaction, End transaction)
BTET is implicit commit mode that is it doesn't require an explicit commit to commit the changes to the DB and ANSI is explicit commit mode.
1) Please check the mode you are using it should be BTET
2) You could also try putting in a NULL statement in between the DDL and the DML by putting in an empty ; or key in an explicit 'ET' statement.