As of WebLogic Server 10gR3, the Type 4 driver for Oracle looks to be deprecated. "Deprecated" means that Oracle|BEA will no longer provide proactive support for the product nor new features. Only security related problem will be fixed and customers are encouraged to migrate to other JDBC drivers(i.e. Oracle Thin Driver).
・The Oracle Driver (Deprecated)
・Using WebLogic Type 4 JDBC Drivers

WebLogic Type 4 driver is an yet another JDBC driver which has been provided by BEA since WLS8.1, and it is actually OEMed by DataDirect. The main focus of the driver is performance and it performs much better than the Oracle's thin driver in many cases. But unfortunately the driver has been immature for long time and sometimes it behaves wrongly. I also strongly suggest using Oracle's Thin driver which is proven to work well.
Customers who wish to continue using the Type 4 driver for some reason can buy an identical driver separately from DataDirect after it's retirement.