SynchronizedMap in Oracle driver?

Question

I am profiling our application with JProfiler and the monitor where we spend most the time block is one to have access to a SynchronizedMap. The problem is that this SynchronizedMap is in the Oracle JDBC driver, like you can see in this stack trace:
java.util.Collections$SynchronizedMap.put()
oracle.jdbc.driver.PhysicalConnection.prepareStatement()
The more concurrency we have in the system, the longer we spend blocked on this monitor. We have different connection pools, with a total of 500+ connections in this test (all established when the application comes up). Also, we are using the Oracle thin driver, version 11.2.0.1.0_ojdbc6. After searching on the web, the only post I found that might be related to this problem is this:
Poor concurrency with Oracle JDBC drivers - Profiler indicates driver-issue
One of my experiments was to make sure that all connections had implicit and explicit caches disabled, so I fetched all the OracleConnection objects and set the cache related properties to disable them. But unfortunately this did not help either.
Has anyone run into this problem before? Would you have any suggestions on how to fix or get around it?
Thanks,
Rodrigo

Answer 1

Hi,
if the SynchronizedMap in PhysicalConnection is not static (I do not have access to the driver source code)it seems that you are sharing one connection among threads beacuse if the map is a class variable there is no need to wait if the connection is shared by one thread at a time.
if you can modifiy your code I suggest you to put a debug instruction (a log call or a println call) just after getting a connection and just before realasing it and check if multiple threads are using the same connection simultaneously.
If so try to follow the following pattern
the thread acquires a connection
the thread uses the connection exclusively
the thread releases the connection
ciao,
Giovanni