Datadomain ( DD) replication across two NBU domain
Hangul2002 is right.
when you use AIR, netbackup inserts inside the backup image the catalog information for the specific backup. The destination server just read this information and import it to his catalog.
This import job is not a regular backup import.No other catalog information is traveling between the master servers. (example tape backup information)
some thoughts.
Probably you can not use AIR with master servers with the same hostname. Using servers with the same name is used if you do storage replication (as you do now with DD VTL) out of the netbackup knowledge or if you use tapes and you must have a way to replicate (or restore) the netbackup database.
If you will use DD with DDBoost and not VTL, then AIR is your way to go. As Nikolai said there is no AIR functionality at the netbackup compatibility list but this is not a problem as OST plugin is a hardware vendor responsibility.
If you want to keep your way, check the recovery without import document. It is updated and cover 7.5. It is harder to do it, probably you will use some scripting, but it is doable.
http://kbdownload.symantec.com/resources/sites/BUSINESS/content/live/TECHNICAL_SOLUTION/28000/TECH28722/en_US/Recovery%20without%20import.pdf?__gda__=1371923810_aa3cf84e6f96f6e9a73990179fc95687
