If a system problem occurs while you're working in a document, the program tries to save your document in a file with the same name and a file extension of .dmp. The program notifies you that an error has occurred, closes all files, and exits. When you next open your document, the program notifies you if the .dmp version of the document is more recent than the .tex version, so you can open the latest version. When you save the document, the program saves it as a .tex document.
To open a .dmp file