yum question: downloaded headers but no updates

[Clint]

Every now and again, I notice that yum will download needed headers, 
which makes me think that an update is about to be done, only to report 
no updates are needed. My yum.conf is mostly a copy of that found at 
artoo, but with an exclude=kernel* line and a seamonkey repo section.

My question is, what is yum doing with the headers if there are no 
updates to be done? Is all of this completely normal operating procedure 
for yum? I'm "curious" about how it's working, rather than "sleeplessly 
concerned" something is going wrong! <grin>

Here is one such example displaying the symptoms that I notice:

# yum update
Gathering header information file(s) from server(s)
Server: Fedora Core 1 - i386 - Base
Server: Fedora.us Extras (Stable)
Server: Fedora.us Extras (Testing)
Server: Fedora.us Extras (Unstable)
Server: Livna.org - Fedora Compatible Packages (stable)
Server: Livna.org - Fedora Compatible Packages (testing)
Server: Livna.org - Fedora Compatible Packages (unstable)
Server: macromedia.mplug.org - Flash Plugin
Server: Fedora Core 1 - i386 - Released Updates
Finding updated packages
Downloading needed headers
perl-Net-SCP-0-0.07-0.fdr 100% |=========================| 1.8 kB    00:00
nvidia-glx-devel-0-1.0.53 100% |=========================| 3.3 kB    00:00
No Packages Available for Update
No actions to take

I didn't see any description of this behavior in man yum. Any insight 
would be appreciated!

Thanks,
Clint

-- 
Clint <clint at penguinsolutions.org>