Online Performance Degradation

I hope someone can help with a performance mystery with an ESQL-C program. We are using Online 4.0 on a Sun 690 w 4 processors, 128M, etc. The process starts up and begins doing transactions from a file (adding data, with lookups) to an empty database. The performance data looks like this: Elapsed minutes: 1 2 3 ... 10 ... 35 ... 50 # of transaction: 220 210 200 150 100 50 If you plot the number of transactions possible against elapsed time you get what looks like a log N graph, ie plotted on log paper you get a downward sloping straight line. I should point out that since we are doing adds, the elapsed time reflects the database getting continuously larger, albeit at a slowing rate. So, the question is: why would performance be falling off in such a drastic and sterotyped fashion? The logN nature must surely be a clue, but I can't fathom OnLine internals. The performance fall-off slows, but since this program is supposed to run briskly over time, I am concerned that the performance might be asymptotic to zero transactions per minute. All of the ESQL-C statements are $prepared the first time they are run, and their cursors $declared. There are hardly any joins (if any at all). There is a table with a combination (2 ints) index. Any help would be most appreciated. Thanks, Andrew Shaw AT&T Bell Labs