cet1@cl.cam.ac.uk (C.E. Thompson) (10/20/89)
In article <8910181519.AA05760@brazos.rice.edu> PERSHNG@YKTVMH.BITNET ("John A. Pershing Jr.") writes >CMS normally runs all programs in (virtual) Supervisor State -- if you >find that you are in problem state, then there is something amiss. > >However, to try to keep you from shooting yourself in the foot, CMS >protects its own storage areas with a Storage Key of x'F', and sets all >"user" pages to a Key of x'E'. This is probably why you are having >difficulty storing into the CAW. There are a number of ways to get >around this annoying behavior ... All of which he gives correctly. However, there is another point to keep in mind: doing your own I/O instructions, and relying on things like the CAW, is going to stop working when (if) you have an XA mode virtual machine. It is better, where possible, to use the synchronous I/O diagnose instructions. Chris Thompson JANET: cet1@uk.ac.cam.phx Internet: cet1%phx.cam.ac.uk@nsfnet-relay.ac.uk
cet1@UUNET.UU.NET ("C.E. Thompson") (10/20/89)
In article <8910181519.AA05760@brazos.rice.edu> PERSHNG@YKTVMH.BITNET ("John A. Pershing Jr.") writes >CMS normally runs all programs in (virtual) Supervisor State -- if you >find that you are in problem state, then there is something amiss. > >However, to try to keep you from shooting yourself in the foot, CMS >protects its own storage areas with a Storage Key of x'F', and sets all >"user" pages to a Key of x'E'. This is probably why you are having >difficulty storing into the CAW. There are a number of ways to get >around this annoying behavior ... All of which he gives correctly. However, there is another point to keep in mind: doing your own I/O instructions, and relying on things like the CAW, is going to stop working when (if) you have an XA mode virtual machine. It is better, where possible, to use the synchronous I/O diagnose instructions. Chris Thompson JANET: cet1@uk.ac.cam.phx Internet: cet1%phx.cam.ac.uk@nsfnet-relay.ac.uk