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Question

hi,
imagine the following scenario.
user TOM is at site B and using a form to update a few records.
Meanwhile BOB at site A is doing the same on the same table. Suddenly BOB gets the "Could not reserve record" message. (They have encountered a lock)
Q. How can I programmatically inform BOB that TOM is the reason for the lock or vice versa ?
I need to get user from SQL AREA or something possibly?
Product is FORMS4.5 on win 95.
ANy ideas very welcome folks.
Please contribute.
thanks
nik.

Answer 1

At least until Oracle 8.1.7 there is no way to detected who is locking a record. But in Forms you can do
the following (in the next post I will discuss the benefits and limitations) :
- Create a table called user_locks with :
record_rowid rowid (primary key)
lock_id number(10)
user_locked varchar2(16)
datetime_locked date
- Define a database sequence called user_lock_id :
increment by 1
start with 1
minvalue 1
maxvalue 1073741823
cycle
- Create a procedure in the database to handle user locks :
create or replace procedure lock_user_record (
p_rowid in varchar2
) as
v_user_locked varchar2(8);
v_datetime_locked date;
v_lock_id pls_integer;
v_status pls_integer;
v_rowid rowid;
procedure insert_lock (
p_rowid in rowid,
p_lock_id in number
) is
pragma autonomous_transaction;
begin
begin
insert into user_locks
(record_rowid,lock_id,user_locked,datetime_locked) values
(p_rowid,p_lock_id,user,sysdate);
exception
when dup_val_on_index then
update
user_locks
set
lock_id = p_lock_id,
user_locked = user,
datetime_locked = sysdate
where
record_rowid = p_rowid;
end;
commit;
end;
begin
if p_rowid = 'AAAAAAAAAAAAAAAAAA' then
return;
end if;
v_rowid := chartorowid(p_rowid);
begin
select
lock_id,
user_locked,
datetime_locked
into
v_lock_id,
v_user_locked,
v_datetime_locked
from
user_locks
where
record_rowid = v_rowid;
exception
when no_data_found then
select
user_lock_id.nextval
into
v_lock_id
from
dual;
end;
v_status := dbms_lock.request(v_lock_id,6,0,true);
if v_status = 0 then -- Success
insert_lock(v_rowid,v_lock_id);
end if;
if v_status = 1 then -- Record locked by another user
raise_application_error(-20001,'Record locked by '||v_user_locked||' since '||to_char(v_datetime_locked)||' '||to_char(v_datetime_locked,'HH24:MI:SS')||'.');
end if;
if v_status = 2 then -- Deadlock detected
raise_application_error(-20002,'Deadlock detected.');
end if;
if v_status = 3 then
raise_application_error(-20003,'Parameter error trying to lock record.');
end if;
if v_status = 5 then
raise_application_error(-20004,'Illegal handle to lock record.');
end if;
end;
- On Forms redefine the trigger "ON-LOCK" :
lock_user_record(:block.rowid);