>Why do it this way? Because it just leverages code that already exists rather 
>than using special purpose code.

Another reason, I assume, and maybe a more important one: The TRANSWAP tries to 
move frames allocated in the non-preferred area to the preferred area. Such a 
frame might however be fixed, and being used as a buffer in an active I/O. The 
swap-out part, logical or physical, will purge all active I/O (and remember to 
re-drive it once the AS is swapped in again). Now even fixed frames can be 
moved. The swap in will fix the, possibly moved, frame and adjust the frame 
address in the quiesced channel program, then re-drive the I/O.

Hope this has not changed since I learned about it many moons ago.

--Peter Hunkeler




--
Peter Hunkeler

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