i am trying to limit the no of results i get from teh search each time for that i specified the fetchsize value in the header but some how i am getting back all results not the specified size. so i put must understand for the queryconfiguration element i get soap exeception that, must understand element did not get processed.
If your seeing issues with this then it may well be a bug.
If you have some example code that's failing for you I'd suggest logging an issue in JIRA (http://issues.alfresco.com), along with the failing code. This allows us to schedule the fix appropriately.