[AccessD] Database Patent

Drew Wutka DWUTKA at Marlow.com
Fri Sep 7 08:56:24 CDT 2007


Depends.  The shadow database where the live database is updating the
test database would have no down time, it would just be a matter of
switching to the new system.

In the case of the snapshot type, where the test system is developed and
tested with a one time snapshot, the down time is going to be the length
of time it takes to import the new data.

In the case of a mixed environment, the example I gave had a downtime of
about 30 seconds. (The time it took me to swap the linked tables with
imported tables.)

Drew

-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Rocky Smolin
at Beach Access Software
Sent: Friday, September 07, 2007 8:08 AM
To: 'Access Developers discussion and problem solving'
Subject: Re: [AccessD] Database Patent

Drew:

In which of these situations, there would be a brief interruption in
service?

Rocky
 




 	
	

-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Drew Wutka
Sent: Thursday, September 06, 2007 10:41 PM
To: Access Developers discussion and problem solving
Subject: Re: [AccessD] Database Patent

To answer your 'shadow' database question, it depends on how the
developer
wants to set things up.  There are lots of methods.  The 'test' database
with the new design could be a snapshot of the data, so that it is
identical
at the start, but the live and the test are then separate.  In this
case,
the 'data dump' process is tested and approved, and when the new system
is
ready, a final data dump is run (may take more then a few minutes
depending
on the size of the system and speed of the components).  We did this
recently with our production/manufacturing database.  Old system on a
Unix
box, new system on a windows based platform.  Same software (just
different
versions (years apart).  The final data dump, when we were ready to go
live,
took about 2 hours.
(Probably about 50 gigs of data).

You could also design a system that runs both at the same time.  In a
server
based OS, triggers could be put in place that would update the
'shadow' server data.   

Another method would be to create an 'update' script.  Where the shadow
system is a mirror of the live site, and the done to it is a script that
updates the design (modifying data formats as needed), and the final
result
is when that script is run against the live system.

Another method is partial jumpers.  Running the new data in a new
database
and keeping the old data (and format) live in the old system, until you
are
ready to put the whole new system in place.  I did this with the ISFE (a
system I built years ago, and recently updated).  The new ISFE had only
a
handful of tables that the old system used.  So the new database
actually
linked those tables while the new system went out.
The old system worked, with a few processes stuck with old data,
(processes
unnecessary in the new system).  There were several things that used the
old
system, however, but they used the linked tables.  So while they were
still
entering data into the old database, the new database saw all that data,
because it was using the links.  When I was ready to drop the old
database,
it was a simple matter of importing the linked tables, took a minute,
tops.

Drew

-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Rocky Smolin
at
Beach Access Software
Sent: Thursday, September 06, 2007 11:18 PM
To: 'Access Developers discussion and problem solving'
Cc: 'Jack Stone'
Subject: Re: [AccessD] Database Patent

Shamil:

Thanks for your response.  So you see nothing  unique in this patent?
(BTW,
the patent is not pending, but has been granted.) Does this look like
"old"
technology to you?  Is it obsolete technology based on what you describe
below as the current methods of implementing changes in the datamodel?

Just out of curiosity - So during the time that the new datamodel is
being
tested in the "shadow" database, am I correct in assuming that the
real-time
changes that are going on in the production database are also happening
in
the "shadow" database?  That it's a mirror?

Rocky

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