details pls: Dynamic MMap ran out of room

[Mike M <linux-support@earthlink.net>]

Following up this:
http://lists.debian.org/debian-user/2004/05/msg00612.html

I was wondering what this magic is doing:

# echo 'APT::Cache-Limit "25165824";' >> /etc/apt/apt.conf

which works for me, BTW. I have 512MB RAM.

I loaded Woody and was updating as part of the process of
upgrading to testing then to unstable.

How'd you get the number? 

Where is the problem? Testing? It seems so because removing
testing and unstable references from the sources.list 
avoids the problem. Opening up only testing finds the problem.

What is the problem?  I know there's not enough memory
allocated. More details would be interesting (I think).

Oddly, the solution to the problem is well covered in cached
email and the APT HOWTO:
http://www.debian.org/doc/manuals/apt-howto/ch-erros.en.html#s-erros-comuns
What is not covered are the questions above.
-- 
Mike

Moving forward in pushing back the envelope of the corporate paradigm.