Hi Stevan, thanks for your reply...
I used two different methods, I checked V$SES_OPTIMIZER_ENV for SADMIN user and I also used DBMS_SQLDIAG.DUMP_TRACE
for the sql that was performing slow by SADMIN. We have another Siebel system and I can see it is the same here.
I talked to our Siebel developers and they believe that the sql comes from a part that normally should not be executed as SADMIN.
Found this is the Siebel Applications Administration Guide
To begin setting up your Siebel application, you must log in with administrative responsibilities. The
Siebel database server installation script creates a Siebel administrator account that you can use to
perform administrative tasks. The default user ID is SADMIN.
So I assume it should be used to configure Siebel and should not be used for application usage.
So I assume having different settings from application users is expected
If you can, you may want to go ahead and open a service request with Oracle Technical Support. If you look at the grantusr.sql script it really does not do anything special for the SADMIN user when creating it at the database level. That being said as a general principal SADMIN should not be used for routine operations.