We have resolved the issue. As usual in hindsight it seems obvious. One of the processes, a transformxml, had the thread count set at 20. This seemed fine as most files going through were about 3m each. Our Java heap was set at 64g. However new files were introduced, that were in the 3g range. Simple math, 3 x 20=60g. used up for that 1 process. Since there was usually about 200k files flowing through at any one time, memory quickly got exhausted. We put a route attribute, to route these large files to a process that only has a couple of threads, while the smaller files could still filter through the process with 20 threads. Thanks for all the help suggestions. @Hans Feldmann ... View more