Troubleshooting 'Memory Exhausted' Error During Large-Scale XML Sitemap Protocol Generation for Deep Sites

Our 'Free XML Sitemap Generator' is hitting an intermittent 'Memory Exhausted' error on large sites. This specifically occurs during final XML serialization for very deep structures, despite ample server resources, which seems tied to the sitemap protocol implementation.

PHP Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 123456789 bytes) in /var/www/html/sitemap_generator.php on line 452

Has anyone tackled similar memory management issues with large-scale XML sitemap generation, especially concerning recursive sitemap protocol processing? Waiting for an expert reply.