TRUNCATE definition question

Question

After a number of years working in Oracle development I (finally!) start to think about definitions.
According definition of DDL it is used to define the database structure or schema
Is there any other explanation why Oracle defines 'TRUNCATE' as DDL except it deallocates memory (and may be is not such conditional statement as ‘DELETE’)

Answer 1

Bob,
Let's prove the opposite, is TRUNCATE a DML statement? :-)
By definition:
Data manipulation language (DML) statements access and manipulate data in existing schema objects. These statements do not implicitly commit the current transaction.
Source: http://download.oracle.com/docs/cd/B19306_01/server.102/b14200/statements_1001.htm#i2099257
From the other hand:
A TRUNCATE statement does not generate any undo information and it commits immediately.
Therefore TRUNCATE is not a DML statement, hence it is a DDL statement :-)
Ok, let's be more serious.
Let's take a look at the following definition:
The execution of DDL statements differs from the execution of DML statements and queries, because the success of a DDL statement requires write access to the data dictionary.
Source:http://download.oracle.com/docs/cd/B19306_01/server.102/b14220/sqlplsql.htm#sthref3520
I think this is a big difference.
In order to see it you can always turn extended trace 10046, level 12 on and check what goes on in the background when you execute TRUNCATE vs when you execute INSERT/DELETE/UPDATE.
TRUNCATE always updates TAB$ and OBJ$ tables. Now, can we say it changes the data structure? I think yes.
Cheers,
Mihajlo
links added
Message was edited by:
tekicora