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1991-01-16
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ONLY1.SHP
ONLY1.SHP is a shared program which can be used with version 2.26 of
DESQview or above. It sets up a DESQview mailbox and will prevent the
opening of the same program or another program which is running ONLY1.SHP
with the same mailbox name.
The reason you might want to use ONLY1.SHP is that you may have a program
that has problems when more than one copy is run concurrently. Or, you have
two or more programs which would conflict with each other over the use of a
file or hardware device if run concurrently.
For instance you might be running a database that does not have any multi-
user facilites to lock a record or field, which may get confused if two
copies of the program are opened. In another instance, you might have two
different programs that use the same serial port. By using ONLY1.SHP, you
can prevent a program from opening and taking the port away from another
program that is using it.
In order to use ONLY1.SHP, you put the ONLY1.SHP driver in the DESQview
directory and specify the program in the shared program field in Change a
Program. The name of the mailbox you want specify is put in the Data field.
An example would be as follows:
------------------------------------------------------------------
Shared Program
Pathname..: only1.shp
Data......: DataBase
------------------------------------------------------------------
If you were to configure your DataBase program as shown above, the first
copy would open normally, but if you tried to open a second copy with the
first still open, you would get an error message as follows:
______________________________
| |
| Only 1 copy of this program |
| can be run at a time ... |
| (DataBase) |
|______________________________|
At this point, you have to hit ESC and the window will be aborted.
Using DESQview's "/MS" Parameter:
ONLY1.SHP uses small amounts of DESQview Shared Memory. This memory must
always be located in conventional memory (below 640K) so that can always
communicate with other shared programs which might be opened. DESQview
reserves some shared memory by default, but the amount is generally
insufficient to support ONLY1.SHP.
The problem which occurs is that once you have a window open which has been
configured to use maximum memory, and then open a window which loads
ONLY1.SHP, the first window will have to be swapped out so that the shared
memory used by ONLY1 can be put below 640K. When you switch back to the
first window, you will again get swapping. If either of the windows have
been made non-swappable, you may get the message, "A non-swappable window is
in the way".
If you are having swapping problems of this type, when using ONLY1.SHP or
other shared programs, start DESQview with the parameter "/SM:1" as follows:
DV /MS:1
This will reserve an extra 1K of shared memory, which should be enough for
ONLY1.SHP's purposes.
Copyright (C) 1990 by Quarterdeck Office Systems
* * * E N D O F F I L E * * *