Re: Road Map to move a home grown application from RPG to DB2 SQL or to any other data base platform

Hi Vern,

I saw also that there are ISAM APIs that provide ways to get to data in an ISAM setup. Do we mean like CHAIN, READ, READE, etc.?

yes

The same article makes this assertion - "Relational databases <https://en.wikipedia.org/wiki/Relational_database_management_system> can easily be built on an ISAM framework with the addition of logic to maintain the validity of the
links between the tables. "

they could, but ISAM is only one way to implement, what MySQL calls a "stotage engine"

That statement suggests something I've felt all along - that the terms "relational database" and "ISAM" are at different levels - an RDBMS can be built over any of several database frameworks, with, I suspect, varying levels of difficulty in
that implementation. ISAM is one of those several frameworks.

it's not only levels of difficulty, it's related to the available ressources, a computer has. ISAM was optimized for very limited ressources on cpu and main memory. Today we have much more cpu power and main memory and the problem is often to make effective use of it. (next week I'm at a customer where a batch job is running > 24 h, only using < 10% of the available ressources...)

I do believe that we do have an ISAM framework and an RDBMS over it. Any distinctions of those 2 concepts, these 2 different levels of abstraction, are not very important, to my way of thinking.

that's true for the world of DDS described tables. These are ISAM tables and the old query engine (CQE) is a layer above, representing a RDBMS.
For SQL tables the relation is the opposite way. The ISAM APIs are using a RDBMS (and only a subset is implemented)

The way to the future is to forget ISAM and use higher levels of abstraction to access databases. SQL is only the next step, then there are data access procedures/functions, next level are ORM (object relational mapping) frameworks.

Dieter