efficiency qn - writing and saving xml file
need some advise on the best approach to take and also if any one knows of a any resouce on this subject that exists online?
When a banner displays on my site, the banner display count is recorded in an xml file and the xml file is saved each time
follwing error occures occasionally:
msxml3.dll error '80070020'
The process cannot access the file because it is being used by another process.
/globalincludes/incBanner.inc, line 291
 is it better to use a sql server database then xml for recording such data? e.g banner display count could amount to as much as 10000 in a day.
 This continuous and frequent saving of the xml file due to client activity - am i using xml for an inappropriate purpose? I had initially done this to reduce the hits on our sql server.
looking forward any valuable replies.