How can I prevent my iPhone from switching to standby while I'm using a specific application.

I am uncertain what you mean by “switches to standby”.

Check with the app maintainer, as it would appear they’re not handling a network switch gracefully.

Apple doesn’t provide a means to dedicate a specific app to a specific network path.

fritstims wrote:

Dear mr.Hoffman. By standby I mean the iPhone switches off to simple smart phone listening setting.

The screen locks, you mean?

I use my phone in a shop, using the shops specific application. It allows me to make a shopping list, scan the products I mean to buy with the iPhone camera and pay for them, on leaving shop. The application needs to be connected to the shops WiFi network, which I authorize on entering. During shopping my iPhone switches off, I lose my shopping list memory content and WiFi connection. I am looking for a way to stop the switch to "dead" while I am using the application. Thank you for help. Frits.

That’s (several) issues with the app, not the least of which is that the developer seemingly never tested the app in practice.

That's a problem with the way the app is coded.

I have what sounds like a very similar app for Giant Eagle grocery stores. I use it pretty much weekly and never have issues when the phone goes into standby. Worst case, it may take a second for it to reconnect to the store WiFi when I wake the phone, but it's never really disruptive.

I'd contact the app developer.