You can provide multiple Sitemap files, but each Sitemap file that you provide must have no more than 50,000 URLs and must be no larger than 10MB (10,485,760 bytes). If you would like, you may compress your Sitemap files using gzip to stay within 10MB and reduce your bandwidth requirement. If you want to list more than 50,000 URLs, you must create multiple Sitemap files.
If you do provide multiple Sitemaps, you should then list each Sitemap file in a Sitemap index file. Sitemap index files may not list more than 1,000 Sitemaps and must be no larger than 10MB (10,485,760 bytes). The XML format of a Sitemap index file is very similar to the XML format of a Sitemap file.
The Sitemap index file must:
Begin with an opening
<sitemapindex>tag and end with a closing tag.
<sitemap>entry for each Sitemap as a parent XML tag.
<loc>child entry for each
<lastmod> tag is also available for Sitemap index files.
Note: A Sitemap index file can only specify Sitemaps that are found on the same site as the Sitemap index file. For example,
http://www.yoursite.com/sitemap_index.xml can include Sitemaps on
http://www.yoursite.com but not on
http://yourhost.yoursite.com. As with Sitemaps, your Sitemap index file must be UTF-8 encoded.
Sample XML Sitemap Index
The following example shows a Sitemap index that lists two Sitemaps:
Note: Sitemap URLs, like all values in your XML files, must be entity escaped.
Comment from: Dialuz Visitor
Very clear explanation of Sitemap Generation, All of my doubts has been clarified. thanks