I'm being part of the development team for migration of a mainframe ERP to Java technology. A preliminary version of the app shows no less than 878 tables (see image). It could be much more, knowing that quite a lot of “lists of values” – which are not supposed to change frequently during the application's lifecycle – were transformed into POJOs containing – well – lists of values. Even on this unfinished version, it was nice to see how Hibernate copes with the level of complexity.
Well, it does scale rather nice. The SessionFactory creation takes about 40 seconds (P4/2.4G/512MB) which is very very decent in this context. The necessary memory for all that metadata and stored statements looks loke a measly \<10MB (altough it's hard to tell, being deeply buried in the entrails of Tomcat - no profiling yet, it's a bit early to invest time in that). And what's more important : our custom app for browsing the database looks as snappier as ever. Next step - when time permits - will be to grind the app a little bit to see if there are any concurrency issues. But so far so good – Hibernate sure looks like a real winner.