> In our "Unix" world we do a full backup monthly, ( 12 months 
> retention ), a differential incremental Monday - Friday ( 14 
> days retention), and a cumulative incremental at the weekends 
> ( 1 month retention ), which satisfies our requirements. We 
> are now starting to migrate our "Windows" world into 
> Netbackup and our immediate plan was to implement the same 
> strategy as used in Unix. However, we have found some 
> documentation which recommends not mixing differentials and 
> cumulatives in the Windows arena. I was hoping that someone 
> could clarify this for me, and if possible explain the reasons why.

Gary - DOS set the "archive" bit in the directory entry on file content
change; this is [everybody's] the default method for finding changed
files on DOS/Windows.  As the PC filesystem grew up, some or all of the
Unix inode info got incorporated into the directory entries (or whatever
MS uses these days).  "c[hange]time," "a[ccess]time" and "m[odify]time"
are available.

You'll find the info you need in the NetBackup System Admin Guides.
Look at the archive bit behavior on full/cumulative/differential and the
options--and their implications--available for using archive bits, ctime
and resetting atime.  You might start with "Determining Files Due for
Backup on Windows Clients" (Windows server SAG I in release 5.1, at
least) for a good overview.