Need suggestions or possible approach for this problem

Question

Hello,
I have a scenario and I want to develop an apex application for this scenario.
The thing is I have mutiple report regions on a page which are querying the same tbl 'loans'. I have a button named 'Assign loan' at the top of the page and at bottom of the page I have buttons 'Save' and 'Complete'. Initially the multiple report regions should not be displayed, only after user clicks on the buton 'Assign loan', then only they should be visible. Similarly for the buttons 'Save' and 'Complete'. After the loan is assigned to a user the button 'Assign loan' should be disabled.
Now Consider a situation where in a user logins to the application and clicks on the button 'Assign a loan', at this point i will update the table and set a flag, so that the user will get that particular record for the reports region. I mean this record should be locked for that user and shouldn't be available for other users. The thing it should work in a multi-user environment, i mean each user should get a different loan when they click the button 'Assign loan'. So, here the user is assigned a loan and he/she makes changes to the multiple report region editable items and he/she can either save the changes by clicking on the button 'Save' or they can click on the button 'Complete' which means the loan was reviewed and is completed. The user shouldn't be assigned an another loan until he/she reviews and completes a paticular loan already assigned to him. And another case would be the user does some changes to the multiple report region editable items and clicks the button 'Save' (menaing pending) the report changes should be saved and he shouldn't be assigned any new loan until he completes the already assigned loan.
Can anyone please help me with their possible suggestions or an approach to this kind of problem.
thanks,
Orton

Answer 1

It looks to me that the trickiest part is preventing more than one user from getting assigned the same loan. I've seen DBMS_LOCK used for a situation like this. It's been years so I'm a bit fuzzy on the exact details but it goes something like this:
When the user clicks 'Assign a loan', try to get an exclusive generic lock:
   dbms_lock.request(lockhandle => 'LOAN_LOCK',
                  lockmode   => dbms_lock.X_MODE,
                  timeout    => 10);If another user already has a lock with this name, try again after the timeout until the lock is obtained (and probably only try a maximum number of times).
Once the lock is obtained, get the next available unassigned loan and set the flag in the table. Now release the lock so the next user can get a loan assigned.
   dbms_lock.release(lockhandle => 'LOAN_LOCK');As long as everyone uses the same process for getting a loan assigned, only the user with a lock can modify the table. The rest of it (the logic around what buttons to show, requiring an assigned loan to be completed before getting another one assigned, etc.) should be relatively straightforward.