As per Google, a sitemap can contain only 5000 Pages in a single sitemap. If you want to create 1M+ pages sitemap, then break it into small parts.
Hi, I am also looking for same SiteMap Generator solution for big websites, but mine is not that big rather i am looking for an auto update version, b'cos I am running a Classified Portal (http://www.bajar.in) which has an mobile version also (http://m.bajar.in). I have generate both sitemaps separately, is there any solution to generate both sitemap at once rather important is to generate sitemap automatically every week. Currently I am using https://www.xml-sitemaps.com but its not upto the mark, it free limit is 500 out-of which it generated me only 300+ links Whereas my portal has more than 5000 pages and links to classified ads and increasing. Secondly I found: http://www.web-site-map.com/ a much better solution Please suggest me, how to keep my sitemap updated regularly, and do i need to update every new sitemap with Google Webmaster also. Thanks & Regards Sharat S.
For larger site. I used to run my own script code to develop sitemaps for each and very category. I merge all the sitemaps in the site map index file. Its better for you also to write your own script as site map generation is very easy.