Re: Timestamp vs Date/time Decimal fields, Overhead in RPG programs...

On 17/03/2010, at 4:33 AM, George Lopez wrote:

From what I heard from Bob Cozzi years many years ago there is a
disadvantage using timestamp field in physical file instead of the
tried and true date and time decimal fields in terms of speed if you are
doing mass update of those fields in an RPG progam? Or is that not
true anymore?

The "overhead" comes from database always presenting date, time, and time-stamp fields in converted human-readable form instead of the internal form. Thus there is an internal conversion from external form to internal form on write/update operations and a conversion from internal to external form on reads. Even DSPPFM, which is supposed to show raw data, does not show raw date. time, or time-stamp data (deliberate design decision).

Any such overhead is not enough to worry about. The benefits of having real date, time, and time-stamp data types in the database far outweigh any performance overhead incurred. By using the proper data types you get easy date/time arithmetic, accurate date calculations, easy conversion from one output format to another, and less actual space used in the file.

Note the use of the phrase "mass updates" in the cited reference? Optimising mass updates (which generally are infrequent) at the expense of normal daily use seems pointless. This is just another performance myth--right up there with "a MOVE of zeroes is faster than a Z-ADD of zeroes".

Regards,
Simon Coulter.
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