Didn't HP fix that (back in the 80's, IIRC) so that when a detail dataset
goes empty, the delete chain gets cleared?

-----Original Message-----
From: Roy Brown [mailto:[log in to unmask]]
Sent: Thursday, February 07, 2002 4:48 PM
To: [log in to unmask]
Subject: Re: [HP3000-L] Image Query


In message <[log in to unmask]>, Steve Belkacem
<[log in to unmask]> writes
>We have two identical image databases, one with data
>and one empty.
>
>Data is extracted from a detail, unsorted dataset with
>only one path to a master dataset to a flat data file
>(we have tried extracting using query, cobol image get
>mode 2, quiz and suprtool). This data in this file is
>then put (by cobol/image) serially back on to the new
>empty database.
>
>When the new database is then accessed the records are
>not actually in the same order as on the original
>database.

Why doesn't the load of the new database fail on the lack of entries in
the master dataset?

But the answer to your question (well, more of an observation, really,
as you don't actually ask a question, but I presume the implied question
is 'why not'?) (and I assume the master above is an automatic one)

is that Image maintains a free space chain for each dataset, and that
free space chain will be utilised first (unless you specify some HWM
jinks, but I suspect you don't).

Your empty database may be empty of records, but it probably
'carries the reminder of every hit that wrote its bytes
  and cut then, as deleted, to its hidden free space chain
  it was leaving, it was leaving, but the blighters still remain'....

So the records you add won't necessarily be added from record 0 in the
detail dataset onwards - the free space chain will be consumed first.

But the serial read *will* be in record number order.

If you delete and recreate your empty database each time, you will start
with an empty free space chain, and so the records will be written in
the record number order in which you add them.

* To join/leave the list, search archives, change list settings, *
* etc., please visit http://raven.utc.edu/archives/hp3000-l.html *