[Info-vax] Indexed file read question

[abrsvc]

On Thursday, 19 November 2020 at 19:07:12 UTC-5, Michael Moroney wrote:
> For whatever it's worth, keys in RMS index files can overlap and be segmented. 
> It's possible for the primary key to be a record number and the secondary key 
> be the record number with a character (A,B,L, blank) appended to the end. Both 
> would have no duplicates but both would be of the same type, likely a character 
> string. You could have a third overlapping key which is just the (A,B,L, blank) 
> if you wanted to find all the "B" records for example. 
> 
> Hardly a gee-whiz Oracle database but it can do a little more than most 
> people realize. 
> 
> Not that it matters since the OP stated this was a migration away from VMS.

I personally understand the use of segmented keys as suggested.  This application was created almost 40 years ago and was not  very efficient.  It uses files as data passing mechanisms and rather than locking, it uses file opens and closes cycling on the open if locked until the open actually happens.  This is not the least efficient mechanism used either.  Indexed files with one record is common too. ARG!!  Anyway, this application could have run on a system 75% smaller than it is and still have extra capacity had it been written correctly.  But as stated, the effort here is to understand the underlying flow such that it can be replaced with more modern hardware.  I got involved way to late to influence the decision.  OpenVMS could easily have remained with some interfacing to PLCs for hardware control, but too late.

Before this thread gets any further from the initial questions, I appreciate the discussion and clarification from all involved.