I ran across a funny thing today in an application I built 10 yesrs ago but that I have not been involved in maintaining since then. The application is gettings som much needed UI upgrades, like getting out of the dark ages and using universal theme.
During that work there were a set of things that didn’t work, components could nbot be found and some unexpected things happened. Unexpected compared to the behavior that had been experienced while doing a mock app in the private environment in the VM.
It turns out the application still has the compatibility mode set to 4.1. Yes, no wonder it was behaving different than when one has 22.x.
This is set during upgrade if upgrading from a version to another where the new has a change in behavior. You’ll want to look into what the change behavior is and make sure your application works well with it so it is on the latest version.
You find this setting in:
Application Properties -> Definition -> Properties -> Compatibility Mode
Oracle has a running lit of the changed behavior version by version in the documentation. That is great so one does not have to find the docs for each version that has changed behavior to find it. It is in one convenient place.
It goes through the changes for each version where the behavior of the APEX engine changed, starting with 4.1 all the way up to the current version. Very convenient to be able to read up on them and see what one should expect and what to check after changing this setting.
As evidenced by this setting in this application having been forgotten it is worth validating that applications you have upgraded has this set to the value you expect. For me I’d expect the latest unless the work to verify that it works as intended has not been completed.