Table lock ? dictionary row lock? recursive?

Question

hi guys,
was looking at dml locks and ddl locks
for example
DML changes to table tab
1) (TX lock for table tab's affected row - stored in the row itself)
2) (TM lock for table tab - store in V$lock)
DDL changes to table tab
1) (DDL lock for table tab -> store in v$lock ?)
2) (TX lock for dictionary affected row -> locking that row in data dictionary tab to reflect changes)
3) (TM lock for dictionary tab -> store in V$lock ?)
(Since i doing a DML to the data dictionary table, am i going to hold another TM lock for that data dictionary table)
what is a DDL lock exactly?
1) a lock on the table tab in v$lock
or
2) or tx lock on the data dictionary row (which will then incurr a recursive TM lock the data dictionary table)
or ?
please advise!

Answer 1

On behalf of Tanel. :)
is that TM lock in v$lock view a DDL lock? (tried an alter table command and saw a TM lock appeared)No, TM lock is dml lock as documented. DDL lock(a.k.a, library cache lock) is not exposed via v$lock view. It's exposed only via x$kgllk view.
so how many locks are actually acquire for e.g when i issue a ALTER TABLE tab xxx ADD col1 NUMBER;You can identify it yourself without big effort.
alter session set events '10704 trace name context forever, level 10';
alter table ...;
alter session set events '10704 trace name context off';==================================
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