Just wanted to offer up a recent lesson learned from an upgrade of an older version of this plugin to the most recent ZC published version (3.9.5). In includes/classes/sitemapxml.php, there was a change/correction in spelling of the constant SITEMAPXML_MAX_ENTRYS to SITEMAPXML_MAX_ENTRIES in all locations of use which is relatively good to see corrected, but also one of those "did it need to be" situations. Regardless, unfortunately for me the site on which the upgrade was occurring used a different setting of 50000 instead of 5000 on line 15
define('SITEMAPXML_MAX_ENTRIES', 50000);
Well, if you focus on the number only as an obvious difference and forget to update the "language" part for that one line (updating all other uses), then upon execution of the code, the value will effectively be undefined and every record will be treated as an individual record rather than a group of records and further as a result, you will generate a file for each such record. Ie. if you have 10000 product in 300 categories, just the product and category sitemap files to be generated, you get 10300 files minimum...
So, be sure that when updating this code from some of the older versions that the entirety of differences are addressed, both the changes in the code as well as the differences applied on the site.
I might have suggested that there be some minimum programmed expectation of the max entries, but really the only reason to have that is in such a clutzy situation of not properly/fully installing the software. I could have just as easily stored the new file and changed the number and been off in the running not to have "learned" this lesson with this program.
