You can predefine all the database connections in the Appeon AEM connection cache first and then dynamically map the transactions to a different connection cache. For details, refer to the pdf attached.  

Also, if necessary, you can go to AEM console | Connection Cache and turn on the dynamic database connection. Once the settings are on, the transaction’s LogPass and LogID will be directly supported and it will allow the end user to change their own username and password.