Replication and synchronizaton of tables over the web. 
Author Message
 Replication and synchronizaton of tables over the web.

I am developing an application in which local branches communicate with a
home office over the web.  Some tables are quite large and would be nice to
have in the local office to search and report on quickly. We would like to
send copies of these tables over the web and update only changed records
when the branches log in.  They are currently free tables, not in a database
container.

Does Fox have built in support for replicating?

Are there third party add-ins which support replication?  Downloadable code
or sample code? Discussions or documentation?

I may go ahead and write the code if I can't find anything soon.  Naively it
seems fairly simple, at least for a couple of tables.  The application would
update home from the branches as it does now ( and would perhaps update it's
own tables with local data by bouncing them through the home office.)
Home would transfer edits by consulting an update date in the record,
records newer than the local record would be transferred.  Home would
transfer adds and deletes by comparing keys with the local office. Keys
missing at the home office would have their records deleted locally, keys
extra at home would be transferred.

Am I missing something(s)?  Are there any deadly gotchas lurking?  Anyone
willing to share smooth or scary experiences?



Wed, 27 Mar 2002 03:00:00 GMT  
 Replication and synchronizaton of tables over the web.
Do look at offline views, as John suggests.  This is a feature of VFP.

In regards of your scenario you present, what happens when the branch office
and the home office edit the same field in the same record.  Example . . .

Branch edits NAME field of record 6 at 2:00 p.m. to read "John"
Home edits NAME field of record 6 at 4:00 p.m. to read "Frank"

Branch logs in and sees record 6 is newer on the Home copy of the table.
The record is copied down to the Branch and now the name field reads "Frank"
even though the Branch changed it to John.  This could cause problems that I
don't think the logic you presented -- granted, very off-the-cuff --
handles.  What about time differences, if any?  You'd have to adjust for
time zones to truly determine which is the latest copy.  And the bottom line
is, just as in simultaneous edits to an optimistically locked local table,
which edit is the one that's "correct"?

What you're thinking about can be a pain.  Offline views have advantages,
but I don't think they are a panacea.

Russell Campbell


Quote:
> I am developing an application in which local branches communicate with a
> home office over the web.  Some tables are quite large and would be nice
to
> have in the local office to search and report on quickly. We would like to
> send copies of these tables over the web and update only changed records
> when the branches log in.  They are currently free tables, not in a
database
> container.

> Does Fox have built in support for replicating?

> Are there third party add-ins which support replication?  Downloadable
code
> or sample code? Discussions or documentation?

> I may go ahead and write the code if I can't find anything soon.  Naively
it
> seems fairly simple, at least for a couple of tables.  The application
would
> update home from the branches as it does now ( and would perhaps update
it's
> own tables with local data by bouncing them through the home office.)
> Home would transfer edits by consulting an update date in the record,
> records newer than the local record would be transferred.  Home would
> transfer adds and deletes by comparing keys with the local office. Keys
> missing at the home office would have their records deleted locally, keys
> extra at home would be transferred.

> Am I missing something(s)?  Are there any deadly gotchas lurking?  Anyone
> willing to share smooth or scary experiences?



Wed, 27 Mar 2002 03:00:00 GMT  
 Replication and synchronizaton of tables over the web.
Have you looked at off-line views?

John/


Quote:
> I am developing an application in which local branches communicate with a
> home office over the web.  Some tables are quite large and would be nice
to
> have in the local office to search and report on quickly. We would like to
> send copies of these tables over the web and update only changed records
> when the branches log in.  They are currently free tables, not in a
database
> container.

> Does Fox have built in support for replicating?

> Are there third party add-ins which support replication?  Downloadable
code
> or sample code? Discussions or documentation?

> I may go ahead and write the code if I can't find anything soon.  Naively
it
> seems fairly simple, at least for a couple of tables.  The application
would
> update home from the branches as it does now ( and would perhaps update
it's
> own tables with local data by bouncing them through the home office.)
> Home would transfer edits by consulting an update date in the record,
> records newer than the local record would be transferred.  Home would
> transfer adds and deletes by comparing keys with the local office. Keys
> missing at the home office would have their records deleted locally, keys
> extra at home would be transferred.

> Am I missing something(s)?  Are there any deadly gotchas lurking?  Anyone
> willing to share smooth or scary experiences?



Thu, 28 Mar 2002 03:00:00 GMT  
 Replication and synchronizaton of tables over the web.
Thanks John.

I am not sure whether or how offline views work over the web.  I am using
West Wind Web Connection.  Does anyone have any experience with this?

John


Quote:
> Have you looked at off-line views?

> John/



> > I am developing an application in which local branches communicate with
a
> > home office over the web.  Some tables are quite large and would be nice
> to
> > have in the local office to search and report on quickly. We would like
to
> > send copies of these tables over the web and update only changed records
> > when the branches log in.  They are currently free tables, not in a
> database
> > container.

> > Does Fox have built in support for replicating?

> > Are there third party add-ins which support replication?  Downloadable
> code
> > or sample code? Discussions or documentation?

> > I may go ahead and write the code if I can't find anything soon.
Naively
> it
> > seems fairly simple, at least for a couple of tables.  The application
> would
> > update home from the branches as it does now ( and would perhaps update
> it's
> > own tables with local data by bouncing them through the home office.)
> > Home would transfer edits by consulting an update date in the record,
> > records newer than the local record would be transferred.  Home would
> > transfer adds and deletes by comparing keys with the local office. Keys
> > missing at the home office would have their records deleted locally,
keys
> > extra at home would be transferred.

> > Am I missing something(s)?  Are there any deadly gotchas lurking?
Anyone
> > willing to share smooth or scary experiences?



Thu, 28 Mar 2002 03:00:00 GMT  
 Replication and synchronizaton of tables over the web.
Hi,
We've done something similar, and the only working solution we found was to
use a database that has GOOD built in support for replication. We used SQL
Anywhere 5.5 and connected via ODBC. Anywhere is doing all the necesary work
for replication, and is supporting replication with SMTP messages (simple
mail over internet). We prefered to a custom build solution because it does
not require any coding, just a judicious database design.
If you consider building a solution of your own, the difficult part is not
the correct functionality, but the zillion of errors you might get: a branch
is not sending it's updates on time, a file is corupted and part of the
updates are applied part are droped etc.
Hope this help,
Regards,

Quote:

>I am developing an application in which local branches communicate with a
>home office over the web.  Some tables are quite large and would be nice to
>have in the local office to search and report on quickly. We would like to
>send copies of these tables over the web and update only changed records
>when the branches log in.  They are currently free tables, not in a
database
>container.

>Does Fox have built in support for replicating?

>Are there third party add-ins which support replication?  Downloadable code
>or sample code? Discussions or documentation?

>I may go ahead and write the code if I can't find anything soon.  Naively
it
>seems fairly simple, at least for a couple of tables.  The application
would
>update home from the branches as it does now ( and would perhaps update
it's
>own tables with local data by bouncing them through the home office.)
>Home would transfer edits by consulting an update date in the record,
>records newer than the local record would be transferred.  Home would
>transfer adds and deletes by comparing keys with the local office. Keys
>missing at the home office would have their records deleted locally, keys
>extra at home would be transferred.

>Am I missing something(s)?  Are there any deadly gotchas lurking?  Anyone
>willing to share smooth or scary experiences?



Fri, 29 Mar 2002 03:00:00 GMT  
 
 [ 5 post ] 

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