"Select * " on 12-18M row table from remote machine thru JDBC - Performance nose-div

On machine 1 - a table that contains between 12 and 18 million rows
On machine 2 - a Java app that calls Select * on the table, and writes it into a Lucene index

Originally had a fetchSize of 10,000 and would take around 38 minutes for 12 million, 50 minutes for 16ish million to read it all & write it all back out as the lucene index

One day it started taking 4 hours. If something changed, we dont know what it was

We tracked it down to, after 10 million or so rows, the Fetch to get the next 10,000 rows from the DB goes from like 1 second to 30 seconds, and stays there

After spending a week of two devs & DBA trying to solve this, we eventually "solved" it by upping the FetchRowSize in the JDBC call to 50,000

It was performing well enough again for a few weeks

then...one day... it started taking 4 hours again

we tried upping the shared_buffer from 16GB to 20GB

And last night... it took 7 hours

does anyone have ANY ideas?!

thanks much