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Quicker way to drop tables and views

These procedures allow multiple sessions to drop tables and views simultaneously to speed up ERP application drop sessions.

ERP application schemas have thousands of tables and views. At our company, it was taking a full hour to "Drop User Cascade." By using 1 Drop_master session and 3 drop_slave sessions, the time was cut in half. These procedures allow multiple sessions to drop tables and views simultaneously. I wrote and used these procedures on an Oracle 9.0.1.4 database. My testing and usage has been against a Peoplesoft install of 12,000+ tables and 6,000+ views.

These procedures are using user_objects to get the name of all the tables and views to drop from a schema. Remember to grant execute on dbms_alert to &Schema_name. We have had good success with 3 slave sessions running.

-----------Begin Script---------------
create or replace procedure 
   DROP_MASTER as
v_msg varchar2(2048);
v_status integer := 10000;

cursor c_obj is
select object_name, object_type from user_objects where object_type in ('TABLE','VIEW');

snapshot_too_old EXCEPTION;            -- Expected condition to ignore
   PRAGMA EXCEPTION_INIT(snapshot_too_old, -1555);
--ORA-01555: snapshot too old: rollback segment number 2 with name "RBS01" too

begin
  dbms_alert.register('A1');
  <<STARTITUP>>
  BEGIN
  for c_obj_rec in c_obj loop
      dbms_alert.signal('A1','drop '||c_obj_rec.object_type||' '||c_obj_rec.object_name);
      commit;
  end loop;
  EXCEPTION
    when snapshot_too_old then
      null;
  end;

--Since messages can be skipped, checks to see if job is done
  select count(*) into v_status from user_objects
  where object_type in ('TABLE','VIEW');

  if v_status <> 0 then         --if it is not done, restart job
    goto STARTITUP;
  else                          --cleanup
    dbms_alert.removeall;
    commit;
  end if;
end;
/

create or replace procedure DROP_SLAVE as
v_msg varchar2(2048);
v_status integer := 10000;

obj_doesnot_exist EXCEPTION;       -- Expected condition to ignore
   PRAGMA EXCEPTION_INIT(obj_doesnot_exist, -942);
--ORA-00942: table or view does not exist

resource_busy EXCEPTION;           -- Expected condition to ignore
   PRAGMA EXCEPTION_INIT(resource_busy, -54);
--ORA-00054: resource busy and acquire with NOWAIT specified

begin
dbms_alert.register('A1');
loop
  dbms_alert.waitone('A1',v_msg, v_status);
  dbms_output.put_line(v_msg||' Dropped');
    begin
      execute immediate v_msg;
    exception
    when obj_doesnot_exist then
      null;
    when resource_busy then
      null;
    end;
end loop;
end;
/
-----------End Script---------------

Reader Feedback

Brian Peasland writes: This is a good tip and the author does some nice error trapping. The only problem I see with it is that it doesn't handle Foreign Key constraints. You can attempt to drop a table and the FK constraint disallows the drop operation.

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