Are you trying to use the 'relocatable database' feature to unmount and move a database to another server? Or just needing to back it up to allow the backup to be reloaded on another server (and keep the database on the original server).
Backup dumps can be performed on any online database just by running 'dump database ...' without preparation. The backup files consume space and can be moved/loaded into another server.
Using the 'relocatable database' feature actually unmounts the the database devices from the original server (writes the information into the manifest file - data remains on the original devices) and allows the devices to be physically moved to another ASE. The database no longer exists on the original server. The manifest file just contains information on how to remount the devices. As such, the devices cannot contain any other database. This is the error you are receiving - in this case the database also on the devices you are trying to unmount is 'master' (you are trying to unmount the master device) but could be any other database.
To unmount a database requires it to be the only database on those devices.
if you are just trying to perform a backup/restore, you should ensure the backup server is running and use 'dump database' on the source and 'load database' on the target..
Chris