RE: Performance of ODBC vs. other access methods

what extra work is needed to admin DB2 on AIX compared to 100% SQL on

i5/OS?

Take a look at slide 60 on this IBM powerpoint:
http://www-304.ibm.com/jct09002c/university/scholars/products/iseries/images
/module8.ppt

There are couple of good sections on slides just before that as well.
That should suffice.

how do MTIs work? Does the system retain ( and maintain ) them once
they are no longer in use? A programmer or sys admin should not have
to keep track of the indexes the database needs to satisfy all the
queries being thrown at it. That is the job of a ton of system code
that runs on a modern, market priced, quad core system.

http://www-03.ibm.com/systems/p/hardware/entry/520q/91311k7a.html

MTIs will be built selectively by the system for the queries used frequently
that could benefit from it.  There are additional cost-to-benefit
considerations before actual decision is made but you can read up on that at
InfoCenter.  Once all jobs/queries that are using the MTI leave the system
and those queries are purged from the plan cache, MTI may be dropped.
Normally though, they'll stick around till IPL.

System will never and should never build all possible indexes.  That is the
job of a DBA.  There is always a trade-off and you can not expect the system
to take everything into consideration.  I mean, what if you (or system per
your contention) build 3000 indexes on your table, and your read-only
queries scream, but your batch process update takes 18 hours?  Should you
let the system make the call if 18 hours for batch update process is
acceptable or should DBA do that?  I think DBA.
Alternatively, if you have a 40 million record table and system kicks off an
index build in the middle of the day and eats up 1 or 4 of your processors
for a long time while building that index.  Is that OK or not?  Again, I
think system should not do it automatically.
Disk space... is it OK to eat up most of your disk space by building indexes
or should you leave some for that pesky data that users need?  Again, a
human call.

Bottom line is that DB2 for System i IS modern database platform and getting
better each day.  It supports core 2003 SQL standards while other platforms
don't yet. 
Biggest benefit is that it is Integrated while none others are.  You don't
have to load it, you don't have to start it, you don't have to purchase it
separately, you don't have to worry about extending database size etc.
And you have joblogs to diagnose issues!  I can't believe other platforms
can't grasp such simple concept.  Did you see call stack exceptions vomited
out by other platforms? Dear God!  Good luck figuring out what went wrong.
Best to click the button saying "Send error report to Microsoft" :)
Or so called 'application logs'?  Why do I need an application log?

I better quit here, getting emotional :)

Elvis