Hierarchical design question

Attention database gurus:

I am currently investigating how to migrate a rather large hierarchical based application running on a DEC VAX to a relational DBMS. The application consists of around 3 million lines of PL1/Fortran code going against a Codasyl (NEXUS) database. It is extremely fast and complex.

I would like to hear from anyone that feels qualified to comment on this effort in general and specifically on the following approach that we are considering:

As it stands today, the application accesses the NEXUS database through a relatively small set of IO routines (between 6 and 10). For this reason, we are thinking about trying to leave the application unchanged and more or less slip NEXUS out and slip the RDBMS in its place. Perhaps the biggest concern with this idea is in the area of performance - assuming for a moment that we could mimmick the existing hierarchical, record-at-a-time architecture - I do not have a good feel for how this will perform (I guess I'm scared to death that it will choke on the heavy volume of transactions).

There are several other serious issues which may doom any approach other than a complete re-design, but the cost savings in this approach is potentially enormous and we are committed to at least trying to build and analyze some sort of reasonable benchmark.

Anyone thoughts/ideas/suggestions/advice or whatever that might help enlighten us would be greatly appreciated. Please direct responses directly to me at connolly_at_udel.edu - I will summarize and post the results.

Thanks,

Tom Connolly
e-mail: connolly_at_udel.edu
voice: (215)359-9858 Received on Sat May 28 1994 - 02:47:46 CEST