From what I understand, oprd is a process dependant on volume manager (vmd). It helps issuing a mount request to the device manager (ltid).
This is what I found in the Media Manager admin guide:
Mounting Media and Reading the Tape Header
The following sequence of operations explains the mount process that is used:
1. vmphyinv contacts the Media Manager volume daemon or process, vmd, on the local
host or remote host depending on where the drive is attached.
2. vmd starts oprd.
3. vmphyinv communicates with oprd and sends the mount request to oprd. After
receiving the request, oprd issues a mount request to ltid.