'omnidbutil' is one of the files installed when you Install the Cell Manager. My guess is that you don't have the Cell Manager installed on the system where you are trying to run 'omnidbutil'
You can check this 2 different ways on the server where you are trying to run 'omnidbutil'
- In Windows Explorer, check to see if the file exists
Program Files -> Omniback -> bin -> bsm
- Go to Services, and check to see if there is a service running 'Data Protector CRS'. This is the service that runs Data Protector. If you don't see this service, then you don't have a Cell Manager installed on this server