There is one thing I like very much about packed decimal data,
that is its redundancy.
With packed decimal data, the probability that the use of an
un-initialized variable will lead to a run time error (0C7 abend)
is very high. Take a nine digit decimal variable - the probability
that it contains a valid decimal representation if all bit patterns
have the same probability is not very high (0.1 percent).
With all binary data types, all bit patterns are valid, and you have
no chance to detect the use of an un-initialized variable (the german
Telefunken hardware had tag bits in storage which allowed for the
detection of such errors even in the binary case - the storage was
initially tagged with a "strange" data type, and so the hardware produced
a so-called "Typenkennungs-Alarm").
I believe that most of the rumour that mainframe applications are
more "stable" than applications on other platforms comes from this
property of the decimal data type, and from the fact, that most
applications are written in COBOL and use this data type, so that
such errors are detected during testing stage.
The more decimal data you have in your applications, the more stable
are your applications. This could also be one of the reasons for
the programming language C being not so stable (among others,
like pointer arithmetic, no control of subscripts etc): the absence
of decimal arithmetic in C - normally.
I'm not sure, if I told you already: in our shop, we run the PL/1
applications
in production with SUBSCRIPTRANGE enabled since some years ago,
and we are very happy with this. The performance is acceptable.
Kind regards
Bernd
Am 14.07.2012 20:39, schrieb John Gilmore:
Although there has been ample tIme to do so, IBM COBOL does not yet
support DFP. It should. When IBM COBOL does support DFP, it will be
possible to eliminate packed-decimal (except as a transitional data
type in certain conversion operations) from COBOL routines; and doing
so will confer large performance advantages.
John Gilmore, Ashland, MA 01721 - USA
----------------------------------------------------------------------
For IBM-MAIN subscribe / signoff / archive access instructions,
send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
