Dear Support Team
We have ACS 5.x, integrated with AD and members are authenticated using either AD username or local username
configured on ACS.
is it possible that ACS checks Local database only when AD is unreachable, customer does not want ACS local database to be used as long as AD is available. it is to fulfill accounting requirements from their System department.
Thanks in Advance for your time.
You are right about everything except the last part, Device Admin 1 and 2 are "Service Selection Rules" so they are going to be matched depending on their Conditions, if the authentication requests is mathing the Device Admin 1 rule then the ACS will stick with this service it doesn't matter if the DB is down or not, ACS is not going to fallback to the Device Admin 2.
The only option to use a second database in case the primary is down is with Identity Store Sequence, however this option will also use the second database if the primary DB cannot find the user.
Unfortunately there is not an option at the moment to accomplish this goal with the specific detail that you need.
Rate if it helps.