Before logging in to Oracle Enterprise Manager Grid Control you will have to start the OMS and ensure that you are in the
$OMS_HOME/bin directory to execute these commands.
$OMS_HOME is the directory where you have installed OMS. However, if you are using Microsoft Windows then you can start the Windows Service for OMS.
emctl start oms
Oracle Enterprise Manager 10g Release 5 Grid Control Copyright (c) 1996, 2009 Oracle Corporation. All rights reserved. opmnctl: opmn started Starting HTTP Server ... Starting Oracle Management Server ... Checking Oracle Management ...