I don't think you need OST anything. You're just doing NDMP to disk (which means it passes through the media server) Or you are doing NDMP to the VTL option in the DataDomain.
OST would be there if you are replicating the DD box, and want to use NBU to control replication via OST/SLP's.
I´m already running OST for all my other ordinary NetBackup-jobs, and if i have understand it correct i can´t mix both OST and VTL in the same Data Domain Box. So i have to get NDMP work with OST.
Jost, refer to below thread, attachments there might help you achieve what you want to configure.
IN a DD box you CAN have both VTL and OST on the same machine.. Go to http://my.datadomain.com for a detailed guide on how to configure VTL with OST.
Yes you need to have a registered account to access my.datadomain.com.
Yes DataDomain allows you to use BOOST/OST, CIFS, NFS, and VTL all at the same time (Which is very cool as no one else allows this!)
However VTL is NOT supported with OST. OST is catalog aware replication that is managed through the backup application. This is ONLY supported with Ethernet and specifically the OST protocol. If you setup VTL, you need to configure replication within the DataDomain boxes using pool replication. At this point, NBU will not be catalog aware of the replication taking place.