This posting Effect Of Multiple SHMMAX Settings at the AskDba.org Weblog is useful in itself, but points out something I learned back in my days as a DBA that is of wider utility: Computers are dumb. Yes, I know they seem smart enough, but if you tell them in a batch file: Pour coffee. Put cup in coffee machine filling bracket, that's exactly what they'll do: Pour the coffee all over the floor and then drop the cup in place. The duplicate settings problem can be especially vexing. It reminds me of a time a friend of mine played a CD. Only something completely different played than he had expected. He took out the CD, looked at it, and only then realized that there had been a CD already in the drive and he put the new one in on top of it. Silly error? Perhaps, but things happen. Scripts are prone to this kind of error, and all the more prone if you don't document changes. Let's say Oracle Support solved a problem you were having in 10.2.0.3 by giving you an underscore parameter. You put it in your initialization parameters and all is good....at least until you move to 10.2.0.5 and find whackiness breaking out all over the DB. If you documented things you will find the date and reason that unserscore parameter was set and comment it out. If not, you may have to do a lot of exploring before you remember that change and track down why it is there and why it has kept you up nights all week.
Every few years (well every few months, really) another death knell sounds for the relational model. Trouble is, it's based on solid math and just doesn't die off. Other bright attempts, however, like the hierarchical database and its stepchild the object oriented application-implemented approach, seem to haunt us regularly, but they never quite measure up to reality. The relational model, of course, is not implemented as theoretically envisioned, in any commercial RDBMS. But the fundamentals are there. This article at ReadWrite Enterprise has some interesting thoughts (in spite of calling tables 'entities' when a relational table is a relation, thus the name: relational): Is the Relational Database Doomed?