If you're airgapped, then the software manager will be unable to work - you'll need to manage your repository and extensions manually (which is not as bad as it sounds.)
With regards to the DAT package, we make a package available on the download page( http://www.mcafee.com/apps/downloads/security-updates/security-updates.aspx ) that you can download and check in to ePO as though it were a product: it will give you the full set of files necessary for the clients to update.
From ePO's perspeecctive, there are effectively two components to a product:
1) the extensions, which allows ePO to
(a) control a point product by creating policies and tasks - this is done by the management extension: and
(b) to understand the events that the point product generates: this is done by the reporting extension
2) the package, which is the install set that ePO uses to install a product on a client machine.
Thus for full command of a product, you need to have the package checked in to the master repository so that you can deploy it, and the extensions checked in so that you can control it. If you haven't already done so, please see the ePO 4.6 Product Guide , specifically the section on Managing Packages And Extensions Manually - it explains this in detail.