Re: Writing an Open Access handle that will either read/write to the Db2 file or make a REST call
Subject: Re: Writing an Open Access handle that will either read/write to the Db2 file or make a REST call
From: "D*B" <dieter.bender@xxxxxxxxxxxx>
Date: Wed, 16 Jan 2019 15:40:27 +0100
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What I have done is to have the OA handler cache the current record as part
of the state info. Any subsequent I/O related to that record is retrieved
from that cache. A lot of the time (as in OP's case) a handler is required
for specific purposes and is best done by not trying to boil the ocean but
rather designing for the task at hand. If you need to go further and create
a generic handler that is a different animal and does indeed present a great
many additional challenges. But it has been done by several people. Lab
Services have an OA "product" that they offer as part of a service
engagement that completely handles all RLA aspects and maps down to SQL. Dan
Cruikshank has described the process and right now we're trying to find
where IBM have hidden the source code.
caching last read record might help for chain/update, but is not sufficient
for going on with reade, readpe ...
once replacing a f punching card with an OA handler, you would have to
provide all I/O operations by your handler and that's the real problem, I'm
Providing some logic for "specials purposes" I would not recommend OA
handlers, because the resulting code is not readable and maintenance is
difficult and error prone.
what really would be needed is an open source solution for replacing RLA by
SQL with minimized effort.
Some additional remarks: First heared of OA, my idee was to have a generic
OA handler translating all rla operations to SQL, with the final goal to
enable existing RLA programms to use true SQL indexes. This would decouple
RLA programms from the database without major changes, opening up the
possibility for redesign steps of the database.
See above. IBM normally do it as part of a database modernization for
exactly the reasons you describe.
I've never seen this at any customers site!!!
What I've seen sold as "modernization" is:
- replacing dds by sql ddl for physical files
- adding autoincrement primary keys and some automatic timestamps and user
- adding some not needed indexes
- adding the (altered) dds logicals. needed for the rla programms to work
costs: lots of money
- more complexity
- referential problems (delete / insert cached record creates duplicate
- no decoupling effect
The next, more importent step to replace rla by SQL to a true view layer to
decouple is never done!!!
This thread ...
Re: Writing an Open Access handle that will either read/write to the Db2 file or make a REST call, (continued)
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