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ORA-06511 PL/SQL: cursor already open

Posted on 2002-06-17
6
3,647 Views
Last Modified: 2012-05-04
Hi all,

Why doesn't the following code return ORA-06511 as I would have expected?

Thanks.

CREATE TABLE blah (col1 NUMBER);

DECLARE
   PROCEDURE do_something IS
      CURSOR c IS
         SELECT *
           FROM blah;
     
      r c%ROWTYPE;
   BEGIN
      OPEN c;
      FETCH c INTO r;
      IF (r.col1 != 50)
      THEN
         RETURN;
      END IF;
   END do_something;
   
BEGIN
   EXECUTE IMMEDIATE 'TRUNCATE TABLE blah';
   FOR i IN 1..5
   LOOP
      INSERT INTO blah
      VALUES (i);
   END LOOP;
   COMMIT;
   FOR i IN 1..10
   LOOP
      do_something;
   END LOOP;
END;
/

DROP TABLE blah;
0
Comment
Question by:Kong
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6 Comments
 
LVL 3

Expert Comment

by:mnicoras
ID: 7084685
Hi,

try this and probably it will tell you more:

CREATE TABLE blah (col1 NUMBER);

SET SERVEROUTPUT ON;

DECLARE
  PROCEDURE do_something IS
     CURSOR c IS
        SELECT *
          FROM blah;
     r c%ROWTYPE;
  BEGIN
-- the part I add
     if c%isopen then
       dbms_output.put_line('cursor is open? '||'true');
     else
       dbms_output.put_line('cursor is open? '||'false');
     end if;
-- the part I add
     OPEN c;
     FETCH c INTO r;
     IF (r.col1 != 50)
     THEN
        RETURN;
     END IF;
  END do_something;
BEGIN
  EXECUTE IMMEDIATE 'TRUNCATE TABLE blah';
  FOR i IN 1..5
  LOOP
     INSERT INTO blah
     VALUES (i);
  END LOOP;
  COMMIT;
  FOR i IN 1..10
  LOOP
     do_something;
  END LOOP;
END;
/

DROP TABLE blah;


enjoy,
Marius Nicoras
0
 
LVL 3

Expert Comment

by:mnicoras
ID: 7084687
Hi,

and now try this:

CREATE TABLE blah (col1 NUMBER);

SET SERVEROUTPUT ON;

DECLARE
  PROCEDURE do_something IS
     CURSOR c IS
        SELECT *
          FROM blah;
     r c%ROWTYPE;
  BEGIN
-- the part I add
     if c%isopen then
       dbms_output.put_line('cursor is open? '||'true');
     else
       dbms_output.put_line('cursor is open? '||'false');
     end if;
-- the part I add
     OPEN c;
     FETCH c INTO r;
-- the part I add more
     if c%isopen then
       dbms_output.put_line('cursor is open? '||'true');
     else
       dbms_output.put_line('cursor is open? '||'false');
     end if;
     OPEN c;
     FETCH c INTO r;
-- the part I add more
     IF (r.col1 != 50)
     THEN
        RETURN;
     END IF;
  END do_something;
BEGIN
  EXECUTE IMMEDIATE 'TRUNCATE TABLE blah';
  FOR i IN 1..5
  LOOP
     INSERT INTO blah
     VALUES (i);
  END LOOP;
  COMMIT;
  FOR i IN 1..10
  LOOP
     do_something;
  END LOOP;
END;
/

DROP TABLE blah;

enjoy more,
Marius Nicoras
0
 
LVL 2

Author Comment

by:Kong
ID: 7084760
Thanks Marius,

You're trying to Open, Fetch, Open within the same scope - which results in ORA-6511, that's expected.

I think I've just explained my own question 8-/ is it possible that we're talking about scope here: since the cursor is opened within a subprogram, when that subprogram exits the cursor goes out of scope/is dereferenced and hence garbage collected. The next time OPEN is called, it has been 'implicitly' closed, thus the exception is not raised.

What do you think?

Here's a supporting example, where the cursor is still within the scope of the subprogram, thus raising the exception:

CREATE TABLE blah (col1 NUMBER);

DECLARE
  CURSOR c IS
     SELECT *
       FROM blah;
       
  r c%ROWTYPE;      

  PROCEDURE do_something IS
  BEGIN
     OPEN c;
     FETCH c INTO r;
     IF (r.col1 != 50)
     THEN
        RETURN;
     END IF;
  END do_something;
 
BEGIN
  EXECUTE IMMEDIATE 'TRUNCATE TABLE blah';
  FOR i IN 1..5
  LOOP
     INSERT INTO blah
     VALUES (i);
  END LOOP;
  COMMIT;
  OPEN c;
  FETCH c INTO r;
  FOR i IN 1..10
  LOOP
     do_something;
  END LOOP;
END;
/

DROP TABLE blah;
0
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LVL 48

Expert Comment

by:schwertner
ID: 7085892
Open the cursor with this the code:

IF c%ISOPEN
  CLOSE c;
END IF;
  OPEN c;
0
 
LVL 3

Accepted Solution

by:
mnicoras earned 100 total points
ID: 7089505
Hi,

you have figure out exactly the idea for opened cursors.

it's a different context for cursor when sub-program it's closed. IN your last example the cursor is within the same context of the sub-program's.

Good for you that you understood correctly the problem. "schwertner" suggestion is obvious! you should not forget it, but I think you already know that, otherwise you didn't come-up with this issue.

best regards,
Marius Nicoras
0
 
LVL 2

Author Comment

by:Kong
ID: 7091348
Well done guys, thanks for your help too schwertner.
0

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