You didn't specify your specific O/S version and patch level, nor did you supply your NetBackup version and patch level. I am unable to direct you to the correct manual, nor the correct page number.
Try locating and downloading the Sys Admin Guide Volume One (Vol 1) for your specific O/S and NBU version, and then use the PDF search options to find either ot these:
force_restore_media_server
failover_restore_media_server
You need to read up about both, as they are slightly different.
If you are using Windows and NBU v6.0, details of both of the above can be found on page 538 of the NetBackup v6.0 - Sys Admin Guide Volume 1 (Windows), which can be found here:
P.S. The following links provide further links to all the manuals: