TECH125520 was written for NetBackup 7.0, and I'm hoping you've upgraded to a version far past 7.0.  :)

For 7.5, for example, you would be better off reading Chapter 5 of this Guide:

Symantec NetBackup 7.5 in Highly Available Environments Administrator’s Guide
 http://symantec.com/docs/DOC5183

Good luck!

Thanks Chris.  I've read Chapter 5 of the HA Guide as well before.  It looks pretty much the same as TECH125520 though.  I'm a bit confused around setting up the "common volume".  How is replication going to work? Do I have to set up a separate process for this?   Thanks

Step 5 in "Installing and configuring the primary NetBackup master server" on the HA Guide states to "Move the catalog components to the volume that is replicated to the secondary master server."  

How is this volume going to be replicated to the secondary site - using a 3rd party app, robocopy, etc?  Appreciate if somebody can advise on how this is configured or has previously set this up.  Thanks. 

This kind of storage based replication* can be done by 3rd party volume manager apps**, or SAN hardware based LUN/volume cross-site synchronization and mirroring features.

Basically, things you put inside the special volume/folder is replicated or sync/mirrored to another volume/folder that is currently - or will be - mounted to another NetBackup server.
I.e., files you put in on one end will appear in another end.

* As opposed to NetBackup's own application level based replication such as Optimized Duplication, A.I.R., or simply the good ol' catalog backup/duplicate to offsite tapes.

** Or Symantec/Veritas Storage Foundation