EMH memory core
The EMH memory core was the memory storage component of the Emergency Medical Holographic program. 

In 2375, The Doctor consulted Seven of Nine after losing spans of his memory. Seven found that portions of his memory in the EMH memory core had been deleted. Expecting this to occur again, The Doctor arranged for deleted files to be automatically backed up and restored. The next time the files were deleted, the computer restored The Doctor's memory files, and he was able to identify the culprit as Captain Kathryn Janeway. ()
Holographic technology