I know that DB2 LUW version 8 has "connection pooling" that provides a connection concentrator (limits the number of simultaneous connections that can occur). But does it really provide connection reuse in the same manner provided by DB2 Connect or Websphere (or some 3rd party tools)?

If DB2 V8 does have connection reuse, does the built-in DB2 connection pooling require extra jdbc coding, and is it as robust as DB2 Connect? I assume the DB2 V8 connection reuse would only run on the DB2 server, and not on the application server (this is an issue if there are multiple application servers).

I have a customer that is using a type 4 driver with a 3rd party tool that provides connection pooling at the application server tier (there are at least 4 different app servers), but it is not working well (it maybe a jdbc type 4 driver problem, maybe a DB2 problem, or maybe a problem with the 3rd party connection tool). It seems to me that maybe DB2 Connect might provide a more compatible interface (at least they can blame IBM if it does not work).

Any thoughts?

I don't think you can call it "connection re-use" - it's rather "agent re-use". An application still needs to establish and release a connection when it needs to access the database. For this reason only I think the concentrator will have poorer performance as compared with traditional connection pooling since establishing a connection is a costly operation.

So, in my opinion the DB2 connection concentrator cannot be used instead of a traditional JDBC connection pool.