
Notes on the Dual-Ported File-11 ACP			Nov 81

     The Dual-Ported Files-11 system enclosed here was not
included on a previous DECUS tape (although I mailed a copy
to anyone who asked for it) because my company made
occasional noises about trying to sell support for it. Since
it was developed for NASA, it is in the public domain and
can't be sold itself.  This version is for RSX-11M version
3.2, it will soon be sort of obsolete. That is, unless no
code changes are made to F11ACP for RSX version 4.0. 
Judging from past experience, (they changed the code between
3.1 and 3.2), F11ACP will undergo enough changes to make the
enclosed package obsolete. 

    The enclosed code is useless without the source to the
3.2 F11ACP, which is only available if you purchase a source
license.  (The 3.1 version was easier to distribute because
the F11ACP source was included in the standard distribution
kit.)  I can't give out the modified DEC written routines,
only SLP files to modify them, so you need the DEC source
for SLP to modify. 

    I hope by giving this software wider distribution
somebody else might pick up the ball and do the RSX 4.0
conversion. If you want to try, tell me, call or write, my 
address is below. I will probably want it and I may be able
to help you with questions that come up.  There's also the
chance that more than one person will want to do it, maybe
the work can be shared, so call me if you don't want to
duplicate efforts. I may not be able to do the conversion
myself, NASA may not be spending very much for contract
programmers next year (you know, budget cuts). 

    This code has been in daily use at NASA/Ames Research 
for a few years now without any major problems.  There may 
be a few quirks.  Occasionally unexplained things happen
such as after being mounted for a week with no down time,
the slave processor has trouble accessing the disk.  But 
dismounting the disk on the slave side, and remounting 
it usually clears up any problems.   But we haven't 
corrupted a disk because of this software since the 
debugging days (almost two years for the RSX 3.2 version).

    Note that this code does nothing at the driver level to 
implement dual-porting.  A SLP file for the 3.2 DB driver 
(RP04, RP06) (the one we use) is included as an example.  I
also did a driver mod for DM's (RK06, RK07), but it worked 
so poorly that I am not including it. I blame the RK06/7 hardware 
design, the hardware people can blame me if they want, but I 
don't recommend those disks for simultaneous dual-porting.
I haven't tried any of the other disks, but a glance at the RM03 
documentation says it ought to work as well as the RP06.


			Dan McCoy
			    (415) 965-6134

			c/o Informatics Inc.
			1121 San Antonio Road
			Palo Alto, California, 94303
