Some times WLS show this error in myserver log:
Could not execute JDBC batch update
And after that nothing work!!
My other question is why, when users  want to login (I
thing when hibernate.cfg wants to create its
connection and it's ...) it makes several Seconds!!
(About 10 Sec.). Is it naturally or not? (When I used
EJB 2.0 or DAO there wasn’t this delay!)
About MR Arghand’s comments:
So thanks for your attentions and reply,
1-How can I change my pooling method for connections?
2-i checked oracle  query caching and response speed of
my application,I don’t think that there is a problem.
3- Can we have your version of Weblogic?
4-i change WLS JVM to JRockIt, but my problem  still
exists!