Appl. Performance degraded after upgrade from PB7.0.2 to PB11.5.1

[mucnivasun]

Currently, we have our applications in PB7.0.2, connecting
to Oracle 10g database( using native driver 'O84 ORACLE
v8.4' + Oracle 9i client).
SQLCA.DBMS = 'O84 ORACLE v8.4'
SQLCA.LogID = gs_userid
SQLCA.LogPass = gs_userid
SQLCA.ServerName = gs_connectstring
SQLCA.AutoCommit = FALSE
SQLCA.DBParm = 'PBDBMS=1'
CONNECT using SQLCA;

We have upgraded the application to PB11.5.1 and connecting
to same Oracle 10g database (using native driver 'O10 ORACLE
10g' + Oracle 10g Client).
SQLCA.DBMS = 'O10 ORACLE 10g'
SQLCA.LogID = gs_userid
SQLCA.LogPass = gs_userid
SQLCA.ServerName = gs_connectstring
SQLCA.AutoCommit = FALSE
SQLCA.DBParm = 'PackageProcs=1'
CONNECT using SQLCA;

After upgrading, the application performance is degraded
drastically. Is there any option to improve the performance or PB will have this much (400% time delay) after upgrade? Please help us on solving the issue.

Regards,
M.Srinivasan