Thanks for response. When we increased the memory limit from 2gb to 20 GB for a process it went fine. datastructure was taking around 30 MB. we broke the datastructure and wrote to disk using storable module. main issue while writing xml file using XML::Simple. xmlOut method expects all contents in one data structure. it would have been better if we can write like streaming or inside loop. is there any way to create xml file in append mode using xml::simple?