cursor problem

Hi, all

there is an application below:

declare
 cursor c1 is
   select id,phone_nbr,work_order_nbr,acct_nbr    from cw_tb
   where work_order_nbr>=' ' and
   acct_id>='A00001' and acct_id<='A09000'; r1 c1%rowtype;
begin
 open c1;
 loop
   fetch c1 into r1
......
......(some DML)
......

here come the problem..
when I use cursor,ORACLE will lock the table in exclusive mode or share mode??

   ( in this exam. the table cw_tb will be locked in shared or exclusive? )

P.S I tried divide this AP to three small range,and ran on three different clients one by one.

       i.e client1 open cursor c1 and acc_id>='A00001' and acc_id<='A03000' and

            client2 open cursor c1 and acc_id>='A03001' and acc_id<='A06000' and

            client3 open cursor c1 and acc_id>='A06001' and acc_id<='A09000'

       but I find that client2&client3 will wait until client1 finish
                        and client3 will wait until client2 finish
                        and client3 will run finally

best regards

Alvin 10/8/1998 Received on Thu Oct 08 1998 - 02:56:09 CDT