We do not have experience in Oracle so if this question is posted in
the wrong area, please respond with the best location for this post...

We are looking for a query that we can run against each of our Oracle
servers that will show each database name, instance name, and all the
schemas. We are trying to build some documentation of our
environment. So far we have been able to determine a list of users by
doing a basic query of dba_users, however we would like to make sure
that we have all databases/instances to drill down into for the user
list. Any suggestions would be appreciated.