Re: Re[2]: Numerics PACKED, ODD format -- Always recommended

[Jon Paris <paris@xxxxxxxxxx>]

>>"PGMs on the AS400 internally default numeric data to packed, translating
zoned
fields before use. Even length packed fields require the first nibble to be
zero, which has no impact on DASD, but which does slightly impact performance.
"<<

Couple of comments.  First only RPG programs exhibit this tendency to convert
everything to packed unless told otherwise.  COBOL, PL/I, C, etc. don't do
this.  I know - I know - RPG is the only language that counts !!!

Second, in most cases the upper nibble of an even length field is only zeroed
when being stored, not whenever it is used.  For this reason it doesn't always
have as much impact on performance as you might imagine.  For example, if you
read a record containing a 6 digit packed field and then use it as the source
in 9 MOVE statements, the overhead would only occur in 10% of the operations
using the field i.e. the one that took the field from the I/O buffer and moved
it into the program's storage area.

Jon Paris - AS/400 AD Market Support - paris@ca.ibm.com
Phone: (416) 448-4019   -   Fax: (416) 448-4414
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