This setting in SUSDB makes patch download go much faster.
It also solves the issue with build and capture if the software update deployment contains to many updates.

From
http://coreworx.blogspot.se/2010/08/configmgr-install-software-updates-task.html

Solution 3

The current number of roundtrips allowed by WSUS is 200 per client session.
The default maximum size of XML data that WSUS allows during each roundtrip is currently 200 KB.
To reduce the number of roundtrips to be within the 200 roundtrip limit per client session, you can adjust the adjust the maximum size of XML data downloads per trip from the 200 KB limit to an unlimited size.

To adjust the maximum size of XML allowed per request, you will need to adjust a setting within the WSUS SUSDB database.
You can adjust this setting by running the following SQL script on the WSUS server:

==========
USE SUSDB
GO
UPDATE tbConfigurationC SET MaxXMLPerRequest = 0
==========

NOTE: You will need to run this on the WSUS/SUP. You should check to see if the SUSDB is hosted by the default Windows Internal Database (WIDS) or by full SQL. You can check the following registry keys on the SUP to determine what is hosting SUSDB:
HKLM\SOFTWARE\Microsoft\Update Services\Server\Setup\SqlServerName