This post was prompted by a comment on my previous post by Alan. If you want to find out which databases are active, log onto the server in question, then you run the following command:
list active databases
To do this you need to log on as a user that has sysadm, sysctrl or sysmaint privileges, e.g the instance owner. You should then be rewarded with output telling you which databases are active with something the looks a little like:
List Activate Databases Output
The full syntax for activating the database can be found here