Re: overlaying arrays in v5r1

Hi Joe

Early in this thread is this statement -

"Since I needed to use the externally described data structure, which brings in the original fields as subfields, I could not create separate data structures to name the subfields again and have them overlaid"

So the problem is, the OP (I believe) could not create a separate DS - and we can't use a field name to lay an array over it - the array would be too large - has to fit in the length of the field being overlaid, if I read the doc correctly last night.

The only concern, as you point out, is that the fields in question do not move in the format - this technique is most useful for non-normalized data such as multiple search fields in a record with the same attributes, instead of being in an auxiliary table with name-value tuples, e.g.

The same comments we've made apply also to non-external DS' using LIKEREC.

As we are encouraged more and more to use data structures for IO, this can become a more-used technique, I think.

Vern

On 1/21/2014 10:00 AM, Joe Pluta wrote:

On 1/21/2014 9:29 AM, Ken Sims wrote:

Oops, my bad! I forgot to mention that when I use this technique, I do
always use a data structure for the record format to ensure that
fields are together in storage as expected. Jon is completely correct
that if you don't use a data structure, there is no guarantee the
fields will be contiguous in storage.

Yes, this is the primary point. If the fields are already in a data
structure (e.g., an E/DS) and you are absolutely sure that the fields
won't move, then creating a based array pointing to the first field is
the way to go.

Otherwise, create your own data structure with the fields and then you
can use either technique, the based array or the OVERLAY array in the
data structure.

Joe