On Apr 24, 5:42 pm, Karl Hanson <kchan...@[EMAIL PROTECTED]
> wrote:
> c0d3...@[EMAIL PROTECTED]
wrote:
>
> <snip>
>
>
>
> > Thanks for the reply, Larry. Yes, The scenario you described is what
> > I'm trying to achieve. The tables will reside on the DB/2 for Linux
> > host, and need to be accessible to the iSeries RPG/CL programs. As
> > for your question about migrating the code, this would play into a
> > larger strategy that allows us to migrate some of the more interesting
> > processes of a legacy iSeries application. The application is way too
> > large to try migrating the entire thing.
>
> > Have you ever tried or seen a similar implementation using the iSeries
> > as a client to any non-iSeries system? Do you know of any issues I
> > should be expecting, such as the differences in security
> > implementations, etc? Performance is already a concern, but all I can
> > do there is measure the differences once I have at least a basic
> > configuration established.
>
> DDM provides a different level of function than DRDA. DDM allows fairly
> transparent trans****t of "file I/O" requests from the System i running
> the RPG application, to a remote System i (for example) that can perform
> these file I/O requests. The RPG program will typically do I/O requests
> such as read by key (SETLL?), read next key equal, read by relative
> record no., etc. As Larry mentioned, these are not SQL operations and
> DB2 for LUW does not sup****t "files", nor this type of file I/O (because
> it is not, and does not map to,
SQL).http://publib.boulder.ibm.com/infocenter/iseries/v5r4/index.jsp?topic...
>
> DRDA on the other hand allows trans****t of SQL requests between systems.
> But since your RPG programs do file I/O and not SQL, DRDA would not
> sup****t your proposal. In other words, there is no function to
> automatically convert file I/O requests to SQL requests, as part of
> either DDM or DRDA. As you correctly surmised, in order to use DRDA
> (SQL), the RPG file I/O would need to be appropriately replaced with
> embedded SQL, or the
equivalent.http://publib.boulder.ibm.com/infocenter/iseries/v5r4/index.jsp?topic...
>
> If the business logic to maintain the data currently resides on System
> i, what is the motivation to move the data to DB2 on Linux? If Linux
> access to data on System i is the goal, could facilities like ODBC or
> JDBC (ie on a Linux client) provide that, w/o migrating the data?
>
> --
> Karl Hanson
The business logic is being migrated in pieces, so not all of it will
reside on the iSeries, but inevitably there will be non-migrated
processes that will still require access to the same files.
My misunderstanding of DRDA and DDM is that I thought DDM was a subset
of DRDA. I was under the impression, any operation a program could
perform using DDM would translate to some function in DRDA and hence
to SQL concepts. Thanks for clearing that up for me.
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