Patent ID: 7904906

Claim:
A method for tracking modified pages in a system comprising a first computer system having a monitor process and a second computer system, the method comprising the steps of: copying, at a first point in time, a memory from the first computer system to the second computer system using the monitor process; tracking, after the first point in time until a second point in time, a process that executes on the first computer system between the first point in time and the second point in time; determining, from the process, after the second point in time, if a page of the memory was modified by the process; copying the page, if modified, from the first computer system to the second computer system using the monitor process; determining if a number of modified pages to be copied from the first computer system to the second computer system can be performed during an acceptable blackout period using the monitor process; halting all processes on the first computer system except the monitor process during the blackout period; copying the number of modified pages from the first computer system to the second computer system using the monitor process; and restarting the first computer system and the second computer system such that the first computer system and the second computer system are in lock step operation.