Siebel server not coming up after Upgrade

After upgrading Siebel to IP2015, the siebel servers are not coming up.  The svc service for Siebel server is starting and after sometime, it is getting killed. Only watchdog process is running. Other processes(like siebmtsh or siebmtshmw or siebproc, etc.) are not starting. Once checking services, we see the below details --
 [parthodas@server1 siebsrvr]$ list_server all
Siebel Server "server1" (Enterprise "TEST_ENT")
started at Wed Jun 22 00:59:19 2016, pid: 2146 (Service process is not running), autostart: no

Issue:- On starting the server, the services are getting killed. No log file is getting created.
The issue is related to encryption issue. With IP2015, Siebel has changed the encryption method from RC4 to AES. So, the old password set at the enterprise level won't work. We need to set the password at the enterprise level and serve level.

• Start Gateway service
• Once Gateway is up, connect to Srvrmgr at enterprise level
                 srvrmgr /g <gatewayhost> /e <enssterprise> /u SADMIN /p SADMIN
  And update enterprise password as below
                 change ent param Password=SADMIN
• Once password is updated, create siebel service file
• Delete the Siebel Server system service using the following command (on Windows, this requires being logged in as user Administrator, or a username that belongs to the Administrators group AND User Agent Control (UAC) disabled):
  siebctl -d -S siebsrvr -i "EnterpriseName_SiebelServerName" (Please change enterprise name and Siebelservername according to your environment)
• Create new siebel service file
  siebctl -h SIEBSRVR_ROOT -S siebsrvr -i "EnterpriseName_SiebelServerName" -a -g "-g GatewayServerHostname:port -e EnterpriseName -s SiebelServerName -u sadmin" -e sadmin

NOTE:--In Windows machine, under certain situation, creation of new Siebel Server service may fail with the following error.

siebctl: Add Service error 1703955

It occurs when the extra registry key exists. Here are the steps to find the and fix it.

•  - Run regedit.
• Locate the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\_BKP_siebsrvr_EnterpriseName_SiebelServerName
  Example: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\_BKP_siebsrvr_sia81_app01
• Export the key for backup reason
• Delete the key

Once it is done, 'siebctl -a' should be able to create new Siebel Server service.

For further details look into the Oracle doc ID 1957428.1.