Configuring "RDP Application Service" in Policy requires administrator to associate Transparent Login Account.
On this screen, before you click on "OK" button, you need to have the Service(in this sample the "Test RDP App") in the upper pane to remain selected.
At the code level, this is by design and was to avoid unnecessary overhead on the PAM while processing the update as there can be hundreds of services in the policy.
By having this selection box checked, only that service will be processed for update.
If you unselect this Service from the upper pane, you will get an error as the Transparent Login Credentials part does not get processed.
This is where you get the error "Error occurred while accessing the database".
The message is misleading but that is the common message that is displayed.
Release : 3.4
Component : PRIVILEGED ACCESS MANAGEMENT
PAM 3.4.0.04 is released to address this issue so the Service does not need to be selected.
A GIF file demonstrating the problem is attached.