A DBMS transparency layer, roughly speaking, is software that makes things that are written for one brand of database management system run unaltered on another.* These never seem to sell well. ANTs has failed in a couple of product strategies. EnterpriseDB’s Oracle compatibility only seems to have netted it a few sales, and only a small fraction of its total business. ParAccel’s and Dataupia’s transparency strategies have produced even less.
*The looseness in that definition highlights a key reason these technologies don’t sell well — it’s hard to be sure that what you’re buying will do a good job of running your particular apps.
This subject comes to mind for two reasons. One is that IBM seems to have licensed EnterpriseDB’s Oracle transparency layer for DB2. The other is that a natural upgrade path from MySQL to Oracle might be a MySQL transparency layer on top of an Oracle base.
At first blush, the Oracle/MySQL possibility could break the mold. Migrating from one product to another product owned by the same vendor is a lot different than migrating from one vendor’s product to another’s. Users have tremendous familiarity with upgrades where one vendor controls both the start and end points of the transition.
On the other hand, the number of cases where a vendor has bought a DBMS product and then migrating a substantial user base over to another DBMS is approximately zero. The template for reasonably successful DBMS vendor consolidations — such as IBM/Informix or Oracle/RDB — is almost always to maintain and enhance multiple product lines side by side.
As for EnterpriseDB/DB2 — if you have an application running on Oracle, why port it to DB2? Unless IBM gets aggressive on its maintenance licensing terms, that won’t even get you much of a first-glance cost saving. And while it’s annoying to do DBA work for two database brands when one will suffice — if you have those Oracle apps already running, then you also already have the DBA resource to keep them going. No doubt there will be situations where this new offering is useful and welcome, but they’ll probably prove to be rather isolated edge cases.
A couple of years ago, I did make a theoretical argument that DBMS portability should become technically easier and hence more widely adopted. But since then I’ve seen very little practical evidence to back it up.