IMP System Change Notification

As most of you probably know, our attempt to release IMPSYS 2600 on May 15 (as discussed in RFC #331) was unsuccessful. Briefly, the primary reasons for failure (all operational rather than programming bugs) were:

1. The network appears to have grown too large for us to successfully coordinate operator intervention at all sites.

2. An unanticipated aspect of the gradual release of the new system was the "poisoning" of IMP's running the new system by adjacent IMP's running the old system, and vice versa. Working around this problem made the dissemination of the new system take much longer than anticipated.

We believe we see solutions to both of these problems and are now ready to schedule the next attempt(s) to release IMPSYS 2600. We hereby request all sites to cooperate with this effort in the following ways.

I. All sites with Model 516 IMP's have been contacted by telephone and

asked to set the switches on their IMP's as follows:

        HALT INH     - off
        W.D.T.       - off
        AUTO RSTRT   - on
        MEMORY PRTCT - off

Please be sure that your switches remain set at these positions until further notice.

II. No site should attempt to use the IMP's "Trace" routine during the

day(s) of the attempted system release.

III. Terminal IMP's may be turned off for significant portions of the

day(s) of the attempted system release. Please be patient with any inconvenience which this causes.

IV. We hope to accomplish release of IMPSYS 2600 on the next attempt.

Nevertheless, we are not omniscient and may again be thwarted by difficulties. Accordingly, we are scheduling the next attempt for Wednesday, May 31, and subsequently every Tuesday (June 6, 13, 20, ...) until the release is successfully accomplished. We will arrange the release process so that site operator coverage is not required; nevertheless we hope that the normal site operator coverage is available in case unanticipated problems develop. Release of the new system will begin early in the day (approximately 7 a.m. EDT). We again suggest that sites do not schedule production work over the network during the release attempt(s). We will notify each site by phone after the release has been successfully completed.

Finally, we apologize in advance for any inconvenience caused by the contortions required to release this new system, and thank all of the site operations' staffs who worked with us on May 15 for their cooperation.

     AAM/jm
     
          [ This RFC was put into machine readable form for entry ]
          [ into the online RFC archives by Ronald de Leeuw 1/99  ]