Summary
This knowledge base article explains how to change the SQL database connection string used in App portal.
Synopsis
In some circumstances, users may want to update the database connection string after installation, for example, when specifying failover parameter. Currently, App Portal UI doesn't provide users with a method to edit the connection string. Please follow the steps below to update the connection string.
Step One: Update connection strings stored in the following files. You may see multiple connection strings in a file. Please update all in that case.
C:\Program Files (x86)\Flexera Software\App Portal\Service\ESDService.exe.config
C:\Program Files (x86)\Flexera Software\App Portal\Web\web.config
C:\Program Files (x86)\Flexera Software\App Portal\APM\Web.config
C:\Program Files (x86)\Flexera Software\App Portal\Utilities\MyApps\AppPortal.App.MyAppsExecutables.exe.config
Step Two:
Restart IIS followed by restarting the windows service called ESDService.
The result:
You can see the updated result as the sample screenshot below: 
Additional Information
In general, connection string is case-insensitive. However, it is reported that several keywords are actually case-sensitive.
The "Failover" keyword is one of them and it is case-sensitive.
https://stackoverflow.com/questions/17306520/sql-server-connection-string-keywords-act-as-case-sensitive-although-they-should
