We have applied Virtual Appliance 14.2 CP2 so we can change the password to the external DB without the need to redeploy the solution.
While the change completes successfully, the applications are unable to start. Reviewing the corresponding logs, we see an error related to incorrect username / password.
The username / password entered in the external DB page are correct and verified.

Identity Suite 14.2
Virtual Appliance CP-VA-140200-0002

It is most likely that the password used for external DB user contains the ! (exclamation mark), the encrypted password value will be incorrect, resulting in incorrect password used by the application server.
Change the DB password so the exclamation mark is not one of the characters or raise a support ticket for a fix.