oracle jdbc driver question

I have a server which makes database calls to retrieve resultset and enumerates through the resultset to create objects (basically doing an OR mapping) and return the objects. The server can be hit with n concurrent users each on a separate thread. The db connections are pooled and I have set the # of connections to be as high as the max possible concurrent users.

It seems when there is a large number of these connections being used concurrently (my test case was 100 concurrent connections), the main performance hit is in the resultset iteration (my test case has a moderately large
number of records as well...500 for each of these 100 users). The fetch method (called by resultset.next()) of the driver marshals and unmarshals each batch of fetches and this (according to optimizeit) hogs the maximum amount of CPU. Increasing the fetch size does not seem to have any significant effect, and the memory used goes up pretty drastically. The other problem area seems to be the resultset.getString. Unfortunately my schema has a large number of strings, so I have to use this often for mapping each row to an object.

Initially, when I saw gc kicking in frequently, I thought that since I am creating a large number of objects to map these 500 rows for each user, I am having this problem. But when I added in an object pool, so that I always have a constant number of objects to map to after the first run, I still have the same problem i.e. large time spent in resultset.next() and resultset.getString

I have somewhat optimized the database and it is now returning all the queries in constant time.
But the time is spent most on the resultset maipulation.

When I brought down the number of open concurrent connections (and users not getting
connections are now waiting till a connection is available back in the pool), the performance improved
drastically. In my test cases, having 10 open concurrent connections seems optimum when I have
100 concurrent users. I am using an oracle db (8.1.7) used locally.

Any ideas if this is a known problem with classes12.zip?

Thanks,
Shantanu Sen Received on Sun Mar 10 2002 - 03:58:18 CST