We are currently using Derby embedded in our web application running on Windows. When processing multiple concurrent requests we have noticed that the Java process handle count continues to increase until the machine becomes unresponsive. I was able to isolate the problem to Derby by running the database in network mode in another process. Further investigation showed that the problem could be reproduced using a select statement that has an IN clause with multiple entries on the primary key column. Spawning multiple threads running the same query causes the handle count to increase considerably on the Derby process. The problem occurs in version 10.1.3.1 and 10.2.1.1 (even worse) in both embedded and network mode. The attached test program duplicates the problem. Start Derby in network mode (using startNetworkServer.bat) and run the enclosed test program. The handle count on the Derby process will increase and never go down short of restarting Derby. Using 10.2.1.1 the handle count for the Derby process goes somewhere between 1400-1500 with just two threads in my environment.