On Thu, 26 Oct 2006 07:31:12 -0400 Peter Relson <[EMAIL PROTECTED]> wrote:
:>>>and I think refreshable implies must be read-only. :>>Also no. :>I disagree. :>Obviously one can write an incorrect program with any attributes. But a :>correctly written refreshable program does not modify itself. :>If the program is refreshable, it means that it can be refreshed at any :>time. And that is exactly what can happen with LPA modules, by the way, if :>any of their real storage has been stolen (LPA modules, after IPL, are not :>"paged out"). They are not refreshed from their data set origin, but from :>the page packs where they were written during IPL. :>Therefore if a program modifies itself at "instant A", then at "instant :>A+1" is refreshed, then that modification is lost, and the program will not :>behave as intended, if you think "intended" would include "expecting a :>change that you made actually to happen". I can think of a case. The program calculates a hash (based on the CPU-id, for example) and stashes that somewhere in common outside the program. It then modifies itself to skip the calculation and use the stored value. Should the program be refreshed, the next pass thru will simply recalculate the same hash and store it again. This would not work if the hashed value is stored within the program. -- Binyamin Dissen <[EMAIL PROTECTED]> http://www.dissensoftware.com Director, Dissen Software, Bar & Grill - Israel Should you use the mailblocks package and expect a response from me, you should preauthorize the dissensoftware.com domain. I very rarely bother responding to challenge/response systems, especially those from irresponsible companies. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
