I could connect to SQL server from my web application on OC4J in hibernate2 version.
with following properties
<property name="connection.datasource">jdbc/MSSQL2K</property>
<property name="hibernate.dialect">net.sf.hibernate.dialect.SQLServerDialect</property>

But i am unable to connect with hibernate 3. Please find Stacktrace of error

--------------------------------------------
hibernate.cfg.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="connection.datasource">java:comp/env/jdbc/MSSQL2K</property>
<property name="hibernate.dialect">org.hibernate.dialect.SQLServerDialect</property>
<property name="show_sql">true</property>
</session-factory>
</hibernate-configuration>
---------------------------------------------

data-sources.xml in OC4j 9.0.4 at
OC4J_HOME\j2ee\home\config


<data-sources>
<data-source
class="com.evermind.sql.DriverManagerDataSource"
name="MSSQL2K"
location="jdbc/MSSQL2K"
xa-location="jdbc/xa/MSSQL2K"
ejb-location="jdbc/MSSQL2K"
schema="database-schemas/ms-sql.xml"
connection-driver="com.microsoft.jdbc.sqlserver.SQLServerDriver"
username="test"
password="test"
url="jdbc:microsoft:sqlserver://raghuveer:1433;DatabaseName=test;SelectMethod=Cursor"
inactivity-timeout="30"
/>
</data-sources>

------------------------------------------------------
ERROR

java.lang.ExceptionInInitializerError
at com.utc.pw.acs.hibernate.dao.CSessionFactory.<clinit>(CSessionFactory.java:44)
at com.utc.pw.acs.hibernate.dao.CLoginDAO.getContactData(CLoginDAO.java:73)
at com.utc.pw.acs.action.CLoginAction.loginCheck(CLoginAction.java:90)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at org.apache.struts.actions.DispatchAction.dispatchMethod(DispatchAction.java:274)
at org.apache.struts.actions.DispatchAction.execute(DispatchAction.java:194)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:419)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:760)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at com.evermind[Oracle Application Server Containers for J2EE 10g (9.0.4.0.0)].server.http.ServletRequestDispatcher.invoke(ServletRequestDispatcher.java:765)
at com.evermind[Oracle Application Server Containers for J2EE 10g (9.0.4.0.0)].server.http.ServletRequestDispatcher.forwardInternal(ServletRequestDispatcher.java:317)
at com.evermind[Oracle Application Server Containers for J2EE 10g (9.0.4.0.0)].server.http.HttpRequestHandler.processRequest(HttpRequestHandler.java:790)
at com.evermind[Oracle Application Server Containers for J2EE 10g (9.0.4.0.0)].server.http.HttpRequestHandler.run(HttpRequestHandler.java:270)
at com.evermind[Oracle Application Server Containers for J2EE 10g (9.0.4.0.0)].server.http.HttpRequestHandler.run(HttpRequestHandler.java:112)
at com.evermind[Oracle Application Server Containers for J2EE 10g (9.0.4.0.0)].util.ReleasableResourcePooledExecutor$MyWorker.run(ReleasableResourcePooledExecutor.java:192)
at java.lang.Thread.run(Thread.java:534)
Caused by: org.hibernate.HibernateException: Could not find datasource
at org.hibernate.connection.DatasourceConnectionProvider.configure(DatasourceConnectionProvider.java:56)
at org.hibernate.connection.ConnectionProviderFactory.newConnectionProvider(ConnectionProviderFactory.java:124)
at org.hibernate.connection.ConnectionProviderFactory.newConnectionProvider(ConnectionProviderFactory.java:56)
at org.hibernate.cfg.SettingsFactory.createConnectionProvider(SettingsFactory.java:366)
at org.hibernate.cfg.SettingsFactory.buildSettings(SettingsFactory.java:60)
at org.hibernate.cfg.Configuration.buildSettings(Configuration.java:1859)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1152)
at com.utc.pw.acs.hibernate.dao.CSessionFactory.<clinit>(CSessionFactory.java:35)
... 21 more
Caused by: javax.naming.NameNotFoundException: jdbc/MSSQL2K not found in Aero Quote
at com.oracle.naming.J2EEContext.getSubContext(J2EEContext.java:93)
at com.oracle.naming.J2EEContext.lookup(J2EEContext.java:76)
at com.evermind[Oracle Application Server Containers for J2EE 10g (9.0.4.0.0)].server.ApplicationContext.lookup(ApplicationContext.java:177)
at com.evermind[Oracle Application Server Containers for J2EE 10g (9.0.4.0.0)].server.ApplicationContext.lookup(ApplicationContext.java:119)
at javax.naming.InitialContext.lookup(InitialContext.java:347)
at org.hibernate.connection.DatasourceConnectionProvider.configure(DatasourceConnectionProvider.java:52)
... 28 more