Hi Miguel Leeuwe

i attached the videoclip with my lab that's using multithread to retrieve some information while the final user is typing.

again i want to thank you so much!

Gosh! I now see your application is PB2019 .. I could have just left it the way I initially made it, jjajaa! Anyway, you have to replace the connection strings in the n_demoMT_connectservice.of_getConnectionInfo() to be something else as "PB Demo DB V2017R3", probably "PB Demo DB V2019" or "PB Demo DB V2019R2" if you're on the beta.
Once you see it all works, then connect to your real database and do some real slow retrievals.

Added info:

I think I got most of the needed information here: 

https://www.powerbuildertv.com/index.php/en/archived-webinars/powerbuilder/162-multithreaded-applications-with-powerbuilder There's a link to download the code and to the presentation by Bruce Armstrong.

Look at the Closequery event of the window. I'm using an instance boolean variable to make sure that you cannot close the window until the multithreading is finished. If not you'd get blow-ups.

Events on the dw_employees control:

retrieveEnd - triggered from the n_callback.of_setdata() function

constructor events of both dw's: to settransobject(sqlca)

window close: destroys, though I'm not sure if that's really necessary.

Also: you'll see that I'm doing the retrieve with 2 string arguments, but they're just there for demo purpose. The final Retrieve() which I'm doing in n_shared.of_retrieve() does not use them.

Okay so here it is, I didn't find my examples, so I've ripped it out from our application at work.

First the video, see the attached file in this answer:

I'm using the demo database of sqlanywhere which comes with PB2017R3, but you can change it to any database you want.

You can see 2 datawindows on the main window. 

The one on the left, I'm retrieving with multiThreading (shared object).

The one on the right is a normal retrieve.

When I first click on the upper command button, the left dw - which has in my demo database more than 120.000 rows (I just duplicated the contents of the employee table a lot of times, after having deleted the primary key) - the multithread retrieve starts. 

Before that one finishes, I click on the lower command button which does a 'normal' retrieve. That one has few rows so finishes early.

You can see that the mt works, because I'm able to click on the lower button, while the retrieve of the first button has not finished yet.

After this answer, I'll upload the sample application made with pb 2017 R3 and give some explanation on the code.

Hi Daniel, I would really like to help.

Can you share the following code snippet?

1. The variable declaration for the transaction object you use in your shared object.
   Incl. whether it is global, shared, instance, or local.
2. The code that creates/assigns a transaction object to this variable.
3. The code that sets up and connects this transaction object to the databse.
4. IF you do embedded SQL THEN => Example of embedded SQL that fails
5. IF you use DataWindow/DataStore THEN => code creating DW/DS; Set-transaction; retrieve data

My gut feeling is one of these places there is a simple typo or misunderstanding or a code line missing. I'm sure both  Miguel and I -- and everyone else reading - hope we fix your issue soon.

Bring it on,
/Michael

You could also try asynchronous retrieve on a second transaction object, but my experience with multi threading is way better, more stable.

As Michael has said, resumed: you need to connect and disconnect in the shared object to it's own transaction object.

If you're stuck let me know, I have some example somewhere, but have to sleep now (Europe), so that'll be tomorrow.

You want database interaction on both your main thread and your background thread in parallel (read: simultaneously)  => You need two DB connections => 2 x SQLCA + 2 x SQLDA + 2 x SQLSA.

These are memory areas that you need to either duplicate or perform thread sync like semaphores or mutex locks. PowerScript itself is straightforward but parallel programming is complex.

HTH /Michael