Splunk DB connect2: unable to restrict identities based on user role

There are two 2 DB connections (say A and B) in our Splunk , I wanted to restrict user access only to "B" database and should not have access to "A" I have created user role and granted read and write permission to "B" DB connection. but the problem here is, Still they are able to access "A" database. looks like, if DBX capabilities granted to a role, then they can access all the db connections. is there anyway where we can have users to access only one connection and not all. I restricted permission at identity level, db connection level but still no luck. Thanks in Advance! Prem