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DLTOBS.TXT
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1991-12-04
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Featured Program
Delete Program Observability
by Bob Cozzi
Each month, Featured Program presents a full-function
command or routine that provides the System/38 user with a
useful tool. Keep in mind that the Featured Program may not
be appropriate for all installations; you must decide
whether it suits your particular needs. Source code found
in the Featured Program can be downloaded via the Q38-IBBS
by dialing (312) 790-5037. Q38-IBBS is available 24 hours
each day, Monday through Friday. The Q38-IBBS is free of
charge to Q38 Technical Journal subscribers.
Most users know the standard solution when they're faced
with a critical disk space shortage: "Buy more DASD!" Well
for years now, a few System/38 users have been retrieving
some of that expensive DASD with a unique feature of the
System/38 MI Assembly Language: DELPGMOBS (Delete Program
Observability.)
The technical description of the DELPGMOBS instruction can
be found in the System/38 Function Concepts Manual:
The [DELPGMOBS] instruction eliminates the capability to
materialize the components, other than the control
information component, of the program template associated
with the program. After deleting observability, only the
control information component of the program template can be
materialized.
In general, the instruction causes the amount of storage
used by the program to be decreased. The amount of storage
released is equal to the size of the program template and
all of its components.
In more common terms, DELPGMOBS is a single MI instruction
that removes the a program's debug template. The numbers
I've seen indicate a reduction in program size of up to 60%.
And, contrary to some advertising claims, programs will not
execute faster.
Who uses DELPGMOBS? Software developers that want to
protect their software from disassembling. There are
software services available that rebuild the high-level
language code from the object. If a program has its
observability deleted, those services cannot be performed.
In addition, the program cannot be debugged, formatted dumps
are not produced, and the program cannot be materialized.
Consequently, if you plan on converting to the System/3x
follow-on, and observability has been deleted from a
program, you will not be able to restore that program onto
the new machine. That is, System/3x follow-on is
object-code compatible, but only if observability has not
been deleted. (You will still, however, be able to restore
source code onto System/3x follow-on.)