The DML versus DDL distinction isn't as clear as their names imply, so things get a bit muddy sometimes.
Oracle clearly classifies
TRUNCATE as DDL in the Concepts Guide, but
DELETE as DML.
The main points that put
TRUNCATE in the DDL camp on Oracle, as I understand it, are:
TRUNCATE can change storage parameters (the
NEXT parameter), and those are part of the object definition - that's in the DDL camp.
TRUNCATE does an implicit
commit, and cannot be rolled back (flashback aside) - most (all?) DDL operations in Oracle do this, no DML does.
The fact that
TRUNCATE doesn't run
ON DELETE triggers also sets it apart from normal DML operations (but some direct path DML operations also skip triggers, so that's not a clear indicator).
That same documentation notes that
DELETE generates UNDO, but
TRUNCATE doesn't, so your statement is correct in this respects. (Note that
TRUNCATE does generate some
REDO so that the truncation can be replayed in case of restore/recovery.) But some
NOLOGGING operations can also produce reduced UNDO (not sure about none at all), so that's not a clear indicator either in my opinion.
So I'd sum it up as:
truncate is not "transactional" in the sense that it commits and can't be rolled back, and can modify object storage attributes. So it's not ordinary DML - Oracle classifies it as DDL.
delete is an ordinary DML statement.