Autonomous Transactions and table locks

Question

Does a commit statement in an Autonomous Transaction block in PL/SQL release locks aquired in the master transaction block?
e.g
CREATE OR REPLACE PACKAGE test_auto_trans AS
PROCEDURE mainproc;
PROCEDURE testproc;
END test_auto_trans;
CREATE OR REPLACE PACKAGE BODY test_auto_trans AS
/*****************Main Procedure*********************/
PROCEDURE mainproc AS
BEGIN
LOCK TABLE a,b,c IN EXCLUSIVE MODE nowait;
/*some processing involving tables a,b,c here. no commit done yet*/
testproc();
/* will the locks on a,b,c still be available here? */
EXCEPTION
WHEN others THEN
dbms_output.put_line('Error');
dbms_output.put_line(sqlcode);
dbms_output.put_line(sqlerrm);
RAISE;
END mainproc;
/*****************test Procedure*********************/
PROCEDURE testproc AS
PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
/*some processing using tables a,b,c here*/
commit;
EXCEPTION
WHEN others THEN
dbms_output.put_line('Error');
dbms_output.put_line(sqlcode);
dbms_output.put_line(sqlerrm);
RAISE;
END testproc;
END test_auto_trans;
/

Answer 1

No transaction will release the locks held by another transaction. When you declare a stored proc to be PRAGMA AUTONOMOUS_TRANSACTION, it is essentially the same as if you logged in as the same user but in a different session.
For example, if I have two sqlplus sessions running as user a, if I do an update in session1 and a delete and commit in session 2 I can still rollback in session 1.
However, your psuedo code as posted will not work at all since the call to test_proc will block until you commit in the main proc, and since test_proc will never return, the main proc will never get to commit. It is exactly analogous to the following:
session1> SELECT * FROM t;
        ID DESCR
         1 One
         2 Two
session1> LOCK TABLE t IN EXCLUSIVE MODE nowait;
Table(s) Locked.
session1> UPDATE t SET descr = 'Un'
  2  WHERE id = 1;
1 row updated.so far, this is your main proc. Now, in another session (which is equivalent to your autonomous transaction procedure), I do:
session2> UPDATE t SET descr = 'Deux'
  2  WHERE id = 2;which as I type is still waiting on the commit from session 1. Therefore, I cannot get to commit the autonomous transaction which would return control to session1
HTH
John
Message was edited by:
John Spencer
Sorry, I initially forgot to answer your actual question "what about DML statements like truncate". Since TRUNCATE is actually a DDL statement I will assume that is what you meant. My initial answer covers DML statements (except SELECT which will work).
All DDL statements in Oracle go
COMMIT
DDL statement
COMMIT
since the initial commit requires a very brief exclusive lock, you will get an error like:
ORA-00054: resource busy and acquire with NOWAIT specified
Exactly as if you did:
session1> LOCK TABLE t IN EXCLUSIVE MODE nowait;
Table(s) Locked.then tried to do it again the another session
session2> LOCK TABLE t IN EXCLUSIVE MODE nowait;
LOCK TABLE t IN EXCLUSIVE MODE nowait
ERROR at line 1:
ORA-00054: resource busy and acquire with NOWAIT specified