no a.out file / mkdir Eunice problem Explained

[Don Libes]

Symptoms:

Eunice's vmsld would not produce an executable, even if there were no
errors.  mkdir would fail saying "couldn't create directory".

Problem:

Eunice uses mailboxes that are globally assigned.  After running
through 300000, the numbers wrap back to 1.  This affects some logic in
the libraries that assume new mailbox #'s are always greater than old.

Comment:

Turns out TWG knew about this problem, but said it happens to very few
customers, since you have to stay up for a long time (or have a lot of
Eunice usage) to have this happen, so they decided NOT TO TELL ANYONE
about this potential problem.  This happened only a few times in the
past 2 years for us, so at first decided it was cosmic rays, but now
that our Eunice usage has increased, its happening more frequently.

Fix:

TWG will send out fixes IF YOU ASK.  Immediate fix is to reboot your
machine.  (Its also been rumored that you can do useful things like
make directories and link programs from DCL, but I've never verified
this.)

Don Libes	{seismo,umcp-cs}!nbs-amrf!libes