Strange Performance Problems

I hope I can get you accurate information here.

We have an LPARed 810 (we have 66% of the CPU) and just recently started to 
notice some slow down. Last Thursday a job that normally takes 15 minutes, 
took 4 hours. Friday and Wednesday (without any changes in between) ran 
normally.Now this last weekend, we did a test upgrade of our ERP software 
and many of the jobs are now taking about twice the time. Here are some 
stats on this:

Step 1: Last time I ran one job at a time and took about 12.5 hours. This 
time I ran 3 jobs at a time and it took 14.5 hours. Now to me, I would think 
that I would save somewhere from 1/2 to 1/4 of the time by running more than 
1 at a time. I know that running 3 at a time will make the jobs run slower, 
but 2 to 3 times slower? This is using straight reads and writes.

Step 2 and 3: These two steps aren't complete yet, but the trend is the same 
about 2 to 3 times slower. Last time I ran 4-6 jobs at a time, this time I 
ran 6 the entire time. I should not be seeing this trend based on the 
numbers I am seeing. This is using this SQL APIs for reads and writes.

So my conclusion is that there is a problem with performance. Our Admin says 
he doesn't see anything. I don't know what all he checked, but I am coming 
to you guys hoping for more ideas. The disk drives (according to WRKDSKSTS) 
aren't being hit very hard. CPU has been running 95+ percent the entire 
time, even though job percentages in WRKACTJOB don't add up to 95+%. 
WRKSYSSTS looks to be normal as well. The Admin said that the cache battery 
isn't low and there isn't a lot of CPU usage on the disk controller. To our 
knowledge, no PTs or other configuration changes have occurred in the past 
few months.

The only major change between the two upgrades is that I upgraded the 
upgrade programs (rather scary that this happens monthly) and some tweaking 
on Lawson's config files, mostly to delivered settings. These settings where 
tested with a single job in this upgrade and took about 1/2 the time to 
process. So I would have expected better performance this time, not worse.

Any suggestions on where else to look for this bottle neck would be greatly 
appreciated!