Bruce,

Isn't that what I said? We were talking about a fully defined item list.
Leonard was just commenting that all of the items of the dataset were
included in the item list and he didn't see where that was any better than
an "@". And in that situation, all of the previously compiled programs would
continue to execute. The only real issue is if an item is deleted from the
database. But then that is another story altogether.

Doug.

Doug Werth                                     Beechglen Development Inc.
[log in to unmask]                                       Cincinnati, Ohio


The opinions expressed do not necessarily represent the views or opinions
of Beechglen Development. They might, but not necessarily. They represent
solely the opinions of the author.

Leonard Berkowitz wrote in his original message:
>>>As a consultant, I saw one application (not where I am consulting now, I
>>hasten to
>>>add!) where list processing was used, but the list of items consisted of
>>every item
>>>in each data set. The combination of the worst of item lists and '@', eh?
>>
>


Bruce Toback replied:

>Older programs will not continue to function without recompile unless
>special precautions are taken. The @ list reads the entire image record,
>and assumes that there's space to do it. Unless you originally allocated
>4096-byte buffers for all IMAGE records (and this IMAGE limit is never
>increased), or unless your program checks the IMAGE record length and
>dynamically allocates buffer space, the newly-added fields will overlay
>some previously-untouched part of the program's data areas. This is
>likely to result in anomalous calculation results or program aborts.
>
>>paring down
>>the item list does not have enough measurable performance impact to
outweigh
>>the derived benefits to maintenance and development.
>
>Again, the benefits to using a named item list are precisely those of
>decreased maintenance and shorter development times. Programs that read
>exactly what they need are immune to changes to items they don't need. In
>the absence of careful documentation -- or when verifying documentation
>-- the only way to determine which fields are used by a program employing
>@-list reads is careful inspection of the entire program source. A
>program that accesses only named items can't possibly touch unnamed
>items, so its interaction with a given database can be ascertained simply
>by inspecting list variables -- or at worst, IMAGE calls.
>
>-- Bruce