Please tell me SQL to see, what tables are locked by which user

Question

could you please tell me the query
so that I can see, what tables are locked by which user in a databse
Thanks

Answer 1

The only way you can ensure that only one transaction touches the data at any one time is to use a select .. for update nowait statement to select the rows to be updated.
Try this::
Where I select the data i want to update in a cursor Incase the row is locked due to any reason it will throw me an error as shown below;
SQL>DECLARE
  2   cursor c
  3   is
  4   select * from emp
  5   where empno = 10
  6   for update nowait;
  7  BEGIN
  8 
  9   for rec in c
10    Loop
11     update emp set ename ='J' where empno = 10;
12    End Loop;
13   
14  DBMS_OUTPUT.PUT_LINE('Record Updated');
15 
16  EXCEPTION
17 
18  WHEN OTHERS THEN
19 
20  DBMS_OUTPUT.PUT_LINE(sqlcode || sqlerrm);
21 
22  END ;
23  /
-54ORA-00054: resource busy and acquire with NOWAIT specified
PL/SQL procedure successfully completed.Edited by: J99 on Jul 28, 2009 4:57 PM