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The "Uncommon File System"
The "Uncommon File System", or UFS, is an unsupported feature of TOPS-10
version 7.03 to facilitate sharing a CI bus among several different
systems. No sharing of disk units or files is provided by this feature.
This feature only assists in preventing access to a disk unit by more
than one system.
(Allowing more than one system to access a disk unit leads to SAT and
directory differences, causing damage to new or existing data on that
disk unit. Co-ordinating this access would require extensive monitor
development which is not planned for TOPS-10 at this time.)
2.0 "DISK SETS"
Inherent in the design of UFS is the concept of a "disk set". A disk
set is a group of file structures which are related. This relation
usually means they belong to the same system. Disk sets are especially
important in the case of CI disks, which can be accessible to several
TOPS-10 systems at the same time.
There are thirty-eight different disk sets. These are the numbered
sets, 1 through 36 (decimal), the "NO" set, and the "ALL" set.
Structures in the "NO" set are never mounted by a system, structures in
the "ALL" set are always mounted by a system, and structures in the
numbered sets are mounted by a system only if the system has been
instructed to mount structures in one (or more) of the numbered sets.
As an example, if system "A" had a system pack called DSKA, and system
"B" had a system pack called DSKB, system A should not be allowed to
access DSKB, nor should system B be allowed to access DSKA. Without UFS
there is no way to prevent TOPS-10 from trying to mount all structures
accessible at ONCE time to the system. Using UFS, you can define DSKA
to be in set 1, and DSKB to be in set 2. Further, you can tell system A
to only mount structures in set 1, and system B to only mount structures
in set 2.
3.0 PARTS OF UFS
Code to support UFS is contained in three places; the monitor, TWICE,
3.1 Monitor Support Of UFS
Whether or not the monitor supports UFS is determined by the conditional
assembly option "FTSETS", defined in the F.MAC file produced by the
MONGEN "F" dialogue. The default setting for this conditional is zero
(or false). By responding "NO" to the MONGEN question "Standard
settings" you can enter the dialogue to change the default setting of
Once you have created a new F.MAC you must re-compile the following
monitor modules: F, COMMOD, ONCE, ONCMOD, and UUOCON. You then proceed
to link the monitor as usual. The result is a monitor with UFS support.
3.2 TWICE Support Of UFS
TWICE is a user-mode version of the ONCE dialogue. The ONCE dialogue
allows the operator to define or change disk parameters. TWICE must be
re-built after re-building the monitor, as TWICE searches F.UNV to
obtain feature test settings.
3.3 GALAXY Support Of UFS
PULSAR has code to GETTAB the conditional feature test flag word in the
monitor which indicates whether the monitor supports UFS. If the
monitor supports UFS, PULSAR will also, and vice versa. No re-assembly
of PULSAR is necessary, as this code exists in the distributed version.
4.0 DEFINING SET NUMBERS WHICH A SYSTEM MOUNTS
There are two ways to define which numbered sets are mounted by the
system. One is intended to be used when building monitors to set a
default, and the other is intended to be used during system start-up
when the default value is not acceptable.
4.1 Via MONGEN
The MONGEN parameter M.SETS defines a bit mask of those numbered sets
which are to be mounted by the system. Bit 0 represents set 1, bit 1
represents set 2, ..., and bit 35 represents set 36. If this parameter
is not specified in the optional octal dialogue, the monitor will not
mount any structures in the numbered sets (i.e., M.SETS defaults to zero
if not defined).
4.2 During ONCE
The optional switch /SETS to the "Startup option" question allows you to
define at ONCE time which numbered sets are to be mounted to the system.
If /SETS is specified, the resulting value over-rides the MONGEN
5.0 DEFINING WHICH SET A STRUCTURE BELONGS TO
The set number is stored in the HOMe block of a disk. The only way to
change the set number is by using the the TWICE program to change disk
parameters. TWICE will ask if you want to change any disk parameters.
If you answer YES, you will be allowed to specify which set number a
structure belongs to. A legal response is either "YES" or "NO", or a
number between 1 and 36 (decimal).
The monitor will not allow you to access a disk unit during the ONCE
dialogue which belongs to a disk set which is not normally mounted to
the system. For this reason, you have to change the set number using
By default, structures are defined as belonging to the "ALL" set; that
is, they will always be mounted by any system which can access the disk
unit(s) which contain that structure. When defining new structures
which are contained on CI type disk units, if you plan to have more than
one system on the CI bus you should plan on putting that structure in a
unique numbered set.
Structures which already exist will belong to the "ALL" set.