> Awesome detailed reply Bob. Thank ! Much appreciated. 

You're most welcome.  Let's see where I could have improved it:  :-)

> 1. You say tapes with errors will be moved to the "none" 
> pool. I was under the
>    impression they would be 'frozen' and left in their 
> orginating Volume Pool ?
>    Can you please clarify what you mean by this.

Sure.  What I meant by 
> >-  Practically, you'll still have a None pool (cleaning tapes,  tapes
> >with errors you don't want used until you test or toss them). 

is that those are popular and well-grounded uses for the None pool--but
you have to put tapes in there yourself; there isn't any automatic
method and you have the error/freeze/leave part correct.  "None" is a
good place for tapes you don't want written to that exists upon
installation.

> 2. What is the "DataStore" Pool actually designed to be used for ?

I should know this, but have forgotten.  It was (is?) another Veritas
product.  Storage Migrator, maybe?

> 3. You mention that cleaning tapes would go into the "None" 
> pool. I was origally
>     thinking of creating a "CLN" pool. Bad idea ?

Nothing wrong with it, just that there's no need, since None handles
keeping them and their *_CLN type visible just fine.  See above.  My
experience has led me to trade heavily on NetBackup's strengths:  let it
handle everything it can (like separating images by retention), rely on
its big-picture scope (like classes, what policies used to be called) to
handle ten or a thousand systems with one set of parameters and free
your brain for more important things, and be parsimonious with pools,
classes, retentions, schedules, ...  it's difficult to watch other users
who just don't grasp that this isn't ArcServe.  

> Oh and another question:
> 
> Why would I need a 'duplicates' and 'catalogue duplicates' pool ?

For sending duplications of backups offsite, or if you want to use Vault
as a model for a homegrown version of it.  The old vault used, by
default, Duplicates for the duplicated images and NBDB-Duplicates for
the accompanying offsite catalog backups.  Bob