[Info-vax] Oracle Database vs Oracle/Rdb

[Arne Vajhøj]

On 6/21/2019 4:48 PM, Stephen Hoffman wrote:
> On 2019-06-19 05:18:04 +0000, DTL said:
>> The Customer wants (why? dunno yet) to "move from Rdb to Oracle" (sic) 
>> in the same environment, with no modifications whatsoever.
> 
> One of the very few database pairings where I'm aware of that being 
> feasible is MySQL to MariaDB, and from MariaDB to MySQL.

Porting between two databases sharing most of the source code
is to be expected to be easy.

> With most other database migrations and including between Oracle Rdb and 
> Oracle Classic?  Nope.  Code changes are required,  The core of the SQL 
> processing will be very similar if not identical, but the rest of the 
> baggage—typically backup and maintenance procedures, any embedded SQL or 
> other DB-specific features, etc—will require code changes.

Regarding application code then it all depends on the application.

It is possible (but maybe not easy) to write portable database code in
most modern languages and frameworks.

The chance that is the case for a VMS application using RDB is probably
small though.

The operational side will definitely be different. There are no
standards for that.

> There are mechanisms that allow querying a remote database from OpenVMS 
> too, and which might provide an alternative to a local database 
> migration.  Much like the database migration, code changes will be 
> required here.  This'll allow use of a newer Oracle database, if that's 
> your choice.  VSI has available a database client for PostgreSQL, as an 
> alternative—that's a PostgreSQL database client for OpenVMS, and *not* a 
> PostgreSQL database server for OpenVMS, some rather confused 
> announcements and postings to the contrary.

Again it depends on the application.

Moving to another platform in this case implies a change
of database.

Arne