Thank you all for the replies.
The reason I ask is that I have a very hard bug / difference to find during
some parallel regression testing.
The subtle difference was finally tracked down to the order that the logical
files were returning records.
The records in both physicals are in the same order (i.e. rrn) but the
logicals return the records differently. One library seems to honour the rrn
theory for records with the same partial key, but the other logical seems to
be pretty random.
Unfortunately for me this is a details file and there is special extra
processing performed on the last detail record, hence the difference in the
regression.
Both files were compiled from the same dds using the same commands params,
they don't reuse deleted records
-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Crispin Bates
Sent: 05 November 2009 20:37
To: Midrange Systems Technical Discussion
Subject: Re: Logical file order of records
Neil,
It depends. What do you mean by identical data?
There was an interesting discussion on the System i network last week
regarding this.
http://forums.systeminetwork.com/isnetforums/showthread.php?t=77551
It is possible that two versions of the same physical, with the same data,
can return the data in different sequences. It really depends on what you
mean by identical data. The data may have been written in a different
sequence, one physical may have been RGZPFM'd. If REUSEDLT(*YES), then what
sequence does the system decide to write to deleted records in?
Don't write applications that rely on data to be sequenced without defining
that sequence as keys. SQL will never guarantee the sequence except for what
is in the ORDER BY. Use the same approach for DDS LF's and you won't get
bitten. If you want to see records in the order they are created, the you
need a Date/Time stamp to sequence them by...
Crispin.
----- Original Message -----
From: "Neill Harper" <neill.harper@xxxxxxxx>
To: "'Midrange Systems Technical Discussion'" <midrange-l@xxxxxxxxxxxx>
Sent: Thursday, November 05, 2009 3:02 PM
Subject: Logical file order of records
If I have a unkeyed PF FILEA as follows:
Field1, Field2, Field3, Field4
I then have an LF LFA, with a non unique key of Field1,Field2,Field3
When there is more and one record with identical Field1,Field2 and Field3
columns, what controls the order of the remaining records.
Further to this, if I had 2 copies of FILEA in different libraries with
EXACTLY the same data in would you expect LFA in both libraries to show
the
records in exactly the same order?
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