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  1.  Home
  2. RPG400-L
  3. August 2010

Arrays and Performance


There is a third alternative which you did not list - usually easier for
you the programmer, and less work for the hardware.

Start with an empty array.
For each lookup, check the array, and if not found then chain to the
database file, and save the retrieved information.
So on each lookup, you do a Check (found/not found), and if needed
(chain and save to array).

Given a normal distribution, most of the time you are re-using the same
lookup values, and are just "re-using" them without the expense of a
Database Chain.


from: " Jonathan Mason
The trouble with this approach is that the arrays are limited in size,
a maximum 9,999 elements in RPG/400 and 32,767 elements in RPG IV.

. . . the first however many records would fit and then chain . . .
. . . make use of user indexes, for a lot more space for storing
entries . . . .

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