%lookup on a Data Structure Array

[Kurt Anderson <kurt.anderson@xxxxxxxxxxxxxx>]

I'm trying to reduce some program I/O for program processing millions of records.  I've identified a file that I feel could be loaded into an array instead of having the program chain out for every record.  Usually this file is between 100-1000 records.  However one of our clients has 20,000 records in the file.  So before making the change, I decided to do a little reading on %lookup, to make sure I'd be using it correctly.
http://www.ibmsystemsmag.com/ibmi/developer/rpg/iSeries-EXTRA--Look-Before-You--Lookup/

It turns out that I had misunderstood how to trigger the binary search with a %lookup.  I thought sorting the array was enough, however to get the binary search one needs to explicitly specify Ascend or Descend on the array.

So I went to add Ascend to a data structure array, and it won't let me:
     D ds_Cust      DS                  Qualified Inz Dim( 50000 ) Ascend
     D  Cust                         3p 0
     D  Cycle                       1a
Error:  RNF3501E Keyword is not allowed for a data-structure definition; keyword is ignored.

I tried adding the Ascend keyword to the subfield that I use in the lookup, but it doesn't like that either (I wasn't expecting this to work, but at this point I'm grasping at straws).

I suppose I could make these two fields their own arrays.  Though I'm not really a fan of that.  I love using data structures to group like-data together.

Is there any way to get the new data structure array lookups to use a binary search?

Kurt Anderson
Sr. Programmer/Analyst
CustomCall Data Systems