Memory dump has nothing to do with graphics performance.
A memory dump occurs when your computer has experienced a serious issue or conflict and Windows in order to protect your computer will suddenly shut down, post a Blue Screen (known as the Blue Screen of Death; BSOD) with an error code, and begin dumping physical memory.
BSODs can be caused by a TON of things like memory corruption, bad drivers or drivers in conflict, etc.
Windows will also create a file to show what caused the system crash. Minidumps are one type of file that when read is very helpful in finding the culprit.