How to split up your large sitemaps?

A sitemap can be split into multiple sitemaps. Your main sitemap will contain a sitemapindex as on the following example:

<?xml version="1.0" encoding="UTF-8"?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
    <sitemap>
        <loc>http://www.example.com/sitemap1.xml</loc>
    </sitemap>
    <sitemap>
        <loc>http://www.example.com/sitemap2.xml</loc>
    </sitemap>
</sitemapindex>