Using 3.6.4 of Hibernate....

Monitoring my application with Introscope. Seeing performance slowdown when the concurrent on my DAO (singleton through Spring) goes from a low of 1 up to 9. The number of active connections in the Weblogic DataPool (around DB2 driver type 4) increases in line with the concurrence. The response times for a particular query go from 30ms to 240ms.

Bottleneck (without doing any monitoring in DB2) appears to be DB2. Question is if there is any way Hibernate acts negatively? If for example the concurrence on a singleton DAO somehow puts a query in a wait state despite the apparent use of an extra connection? The obvious is that the query performs badly because DB2 isn't scaling. More wondering if there is the possibility of something to look for in the Hibernate set-up?

Turns out the bottleneck is not related to Hibernate at all. Rather that there is a large amount of compilation time in DB2. Using XMLEXISTS in my queries and compilation takes over 50% of the total SQL execution time which gets worse with concurrency.