Author: Shack Toms
Technical Advisors, Inc.
4455 Fletcher Street
Wayne, Michigan 48184
(313) 722-5010
Description: DV is a program which creates an ordinary
non-contiguous disk file, and uses the
logical blocks therin as the physical
sectors of an imaginary disk drive.
This virtual disk drive can appear to
IAS as any of the known (to the author)
DEC disk drives. The size of the disk
is up to the user (the virtual disk is
not pre-allocated.)
Complete file control services are available
on the virtual disk. In particular:
INITIALIZE works on it (if it is emulating an allowed
device type)
MOUNT works on it
DISMOUNT works on it
DSC works on it
FLX works on it
In general, everything, works on it except for
disk diagnostics.
Genning for it: To sysgen a virtual disk into your system
edit the [11,17]SYSGEN.CMD file to include
the following directive (with all the other
DEV= directives.)
DEV=DV0,<150010,0,0,1000>,,,,VRTACP
Then perform a system generation.
Building it: Set your default UIC to the acccount where
this file was found. Then type:
PDS> @dv
After a while pds should buzz, and the build
will be complete.
Using it: When a disk is first created, it looks as though
BADBLOCKS had been run on it and found no bad
blocks.
The following command sequence will enable
a virtual disk. The disk will reside in a file
named SY0:[1,1]MYDISK.DSK. It will emulate
an RK05. You probably need various priveleges
to do this.
PDS> install dv
PDS> install/task:vrtacp sy0:[11,1]bigfcp ! [ or fcp ]
PDS> mcr loa dv
Fake disk file? mydisk/create/emulate:rk05
PDS> allocate dv0
PDS> initialize/index:beginning dv0 virt
PDS> deallocate dv0
PDS> mount/nooperator dv0 virt
That should do it.
When finished with the disk, use:
PDS> dismount dv0
PDS> mcr unl dv
To remount the disk, use:
PDS> mcr loa dv
Fake disk file? mydisk
PDS> mount/nooperator dv0 virt
The virtual disk handler remembers that the disk
is an RK05.
I have had much success with this device. I
have many large fixed length record files, with
short record lengths (8 bytes.) The most
efficient way for me to copy these files to
mag tape is to first copy them to a virtual
disk, and then to DSC that disk to mag tape.
Of course, I find that whenever I copy any
files from mag tape to disk (virtual or otherwise),
duing peak activity, there is a great probability
of a system crash. (The mag tape handler apparantly
interferes with disk UMR usage, since the crash
generally appears when a block from mag tape
overwrites a recently loaded task header.)
If you have a habit of running out of UIC's,
you may find this program helps.
For more complete information on the operation
and use of this program, read the blocks of
comments in the beginning of it.