RE: Journaling for data recovery - Lost records.

["Don Tully" <dtully@xxxxxxxxxx>]

All machines (and customers) of mine have used journaling since 1992.  All
systems that I have built since 1995 have used RI on all non-work files.  RI
always requires that parent row be written prior to child row.  If attempt
to write the child first is processed, that will be immediately followed
with a rollback transaction.

Journaling can be very "expensive" if the application is poorly written.  By
that, I mean retrieving of records for update-- requiring record locking--
and updating with the same image or only change is to audit time stamp.  The
old update primary file program where only a very small portion of the
records actually needing to be updated. If those culprit programs are
corrected, journaling has a minimal impact.. maybe in 3 to 5% range.  At
least that has been my experience.

Journaling also provides a gold mine for testing.  Rather than just looking
at some end results, examine the journal and see all of the database
updates.  One is often amazed at updates that would otherwise surely go
unnoticed until down the road and  some seemingly unrelated data problem is
noticed.

I would not want to run without journaling or RI.

Don Tully
Tully Consulting LLC

-----Original Message-----
Subject: Journaling for data recovery - Lost records.

...
On a related topic, what would have happened if we had declared RI
between the invoice detail and invoice detail-detail tables? Would we
now have a child row w/o a parent row?

I told the client that he should turn on journaling on all his files as
standard practice, but I got the old "Journaling is too expensive"
response. I know that has changed over the years, but does IBM have any
whitepapers to that effect?

-Walden

------------
Walden H Leverich III
President & CEO
Tech Software
(516) 627-3800 x11
WaldenL@xxxxxxxxxxxxxxx <mailto:WaldenL@xxxxxxxxxxxxxxx>
http://www.TechSoftInc.com <http://www.techsoftinc.com/>

Quiquid latine dictum sit altum viditur.
(Whatever is said in Latin seems profound.)


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