Reference and Change Bit Recording
Original Publication Date: 1981-May-01
Included in the Prior Art Database: 2005-Feb-11
In a computer system with virtual storage, any reference to data or instructions which do not reside in main storage causes a fixed size block of data or instructions, i.e., a page, to be moved from secondary storage into main storage. In order to accommodate the new page in main storage, it may be necessary to move some other page from main storage to the secondary storage. To aid the page-replacement process, it is desirable to keep track of those pages which have been referenced. A single reference bit for each page is used for this purpose and is set whenever an address in the page is referenced. When a page has to be replaced, the page-replacement mechanism selects a page with its reference bit not set.