On 8-okt-2006, at 1:46, Narinder Chandi wrote:
Can someone point out where I'm going wrong? I have a list of records
displayed in a list box from which I can double click to open
records for
editing in a new window. Each window is opened in its own thread and I
explicitly start a transaction. For the first record opened its OK,
but when
trying to open a second record (in a new thread in a new window) I
get this
error :
"Cannot start a transaction within a transaction"
Hi Narinder,
Here are a few tips:
1. Forget all you learned about 4D. Things like processes, process
variables, interprocess variables do not apply to RB.
2. RB threads are not equal to 4D processes. A 4D process has its won
variable table (process variables). A thread has not. It has acces to
all the variables in your application.
3. There is no sense in opening a new window in its own thread. If
you use something like "Window1.Show" the thread would end right
after the window is opened (assuming there is no other code after
that line). Yes in 4D you would launch a new process to have multiple
windows to interact with. But that is not needed in RB. In RB you
will mostly use threads to do background processing.
4. In 4D each process had its own editing context (selection of
records, transactions etc.) There is no real equivalent when working
with SQL databases. Each recordset can be considered a selection. In
order to have multiple (individual) transactions you need multiple
connections.
5. Don't use transactions as an undo-mechanism as you would in 4D.
Instead store all the relevant data in memory and let the user edit
it. Once the user clicks the save button, you start a transaction
update the relevant records and commit (or rollback) the transaction.
This way you keep your transactions short and lock records only for a
short while.
HTH,
- Rob Laveaux
--------------------------------------------------------
Pluggers Software
Thijssestraat 203
2521 ZG Den Haag
The Netherlands
Email: [EMAIL PROTECTED]
Website: http://www.pluggers.nl
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