I was going thru forums and found out your following solution for memory limit when user cannot modify memory_limit on shared hosting.
if you are not allowed to modify PHP settings to increase memory_limit option, the only way to get the whole site included into sitemap is to try to separate the site on several parts .
For instance, if your site has folders:
you can generate sitemap for every single subfolder (using corresponding "Starting URL" setting) .
It depends on your site structure and may be hard (or impossible) to do in some cases though.
Now I have similar directory structure. So should I generate sitemap for each directory separately like sitemap1, sitemap2,sitemap3,…sitemap100…. and then include all links of all top level directories and links of these other sitemaps in main SITEMAP, Will google crawl my pages if I do it this way?? Is this the right way to do it?