Re: CHAIN on a Partial Key

[Scott Klement <rpg400-l@xxxxxxxxxxxxxxxx>]

Sorry, Charlie...   I use logical files with partial keys frequently.  I 
have never seen "strange things" happen.  They work extremely well and 
efficiently.  And in 30ish years of doing this stuff, I never met 
another programmer that didn't understand them.

Anything you post here, there will be a handful of people who will get 
it wrong, and post it that way.  It doesn't matter what it is -- there's 
always someone.

Don't let that stop you from using useful techniques!

Honestly, I think the people here who think that the sequence is 
unpredictable are confusing CHAIN/SETLL/READE type operations with SQL. 
 In SQL, if you don't specify an "order by" clause, then the sequence 
is unpredictable.  This is not true of the native I/O opcodes.

-SK




On 3/28/2013 2:51 PM, Charles Brewster wrote:
> Crispin,
>
> I am not sure if it is just self-imposed or if I was told by someone
> when I was a young programmer, but I never, never, never chain with a
> partial key on a logical file. Strange things can happen and as we
> see from this thread, it is confusing to the programmers that follow
> behind you.
>
> Maybe it comes down to programming "style."
>
> In my book CHAIN is reserved for when I need to update a record in a
> file, the CHAIN should use a complete key that satisfies all fields
> in a unique logical file.
>
> I use SETLL and READ/READE for everything else. (Sometimes the SETLL
> is enough and you never even need to do the read, performance
> bonus!)
>
> Charlie