OEM 11g Architecture

Stop OMS Services

[oracle@OMS_HOST bin]$ $OMS_HOME/bin/emctl stop oms
Oracle Enterprise Manager 11g Release 1 Grid Control
Copyright (c) 1996, 2010 Oracle Corporation.  All rights reserved.
Stopping WebTier…
WebTier Successfully Stopped
Stopping Oracle Management Server…
Oracle Management Server Successfully Stopped
Oracle Management Server is Down

From the AGENT_HOME directory run the following to stop the Agent.

[oracle@OMS_HOST bin]$ $AGENT_HOME/bin/emctl stop agent
Oracle Enterprise Manager 11g Release 1 Grid Control 11.1.0.1.0
Copyright (c) 1996, 2010 Oracle Corporation.  All rights reserved.
Stopping agent … stopped.

Stop Database

[oracle@OMS_HOST bin]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.1.0 Production on Thu Mar 10 14:38:49 2011
Copyright (c) 1982, 2009, Oracle.  All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 – 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.

Locate name of Listener and stop it

[oracle@OMS_HOST bin]$ ps -ef | grep tns
oracle    1958 18839  0 14:39 pts/1    00:00:00 grep tns
oracle   24736     1  0 Feb10 ?        00:01:28 /opt/app/oracle/product/11.2/db_1/bin/tnslsnr LISTENER -inherit
[oracle@OMS_HOST bin]$ lsnrctl stop LISTENER
LSNRCTL for Linux: Version 11.2.0.1.0 – Production on 10-MAR-2011 14:40:00
Copyright (c) 1991, 2009, Oracle.  All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=OMS_HOST)(PORT=1529)))
The command completed successfully

StartOMS Services

[oracle@OMS_HOST bin]$ lsnrctl start LISTENER
[oracle@OMS_HOST]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.1.0 Production on Thu Mar 10 14:42:43 2011
Copyright (c) 1982, 2009, Oracle.  All rights reserved.
Connected to an idle instance.
SQL> startup;
ORACLE instance started.
[oracle@OMS_HOST]$ $OMS_HOME/bin/emctl start oms
Oracle Enterprise Manager 11g Release 1 Grid Control
Copyright (c) 1996, 2010 Oracle Corporation.  All rights reserved.
Starting WebTier…
WebTier Successfully Started
Starting Oracle Management Server…
Oracle Management Server Successfully Started
Oracle Management Server is Up
[oracle@OMS_HOST]$ cd $AGENT_HOME
[oracle@OMS_HOSTagent11g]$ cd bin/
[oracle@OMS_HOST]$ ./emctl start agent
Oracle Enterprise Manager 11g Release 1 Grid Control 11.1.0.1.0
Copyright (c) 1996, 2010 Oracle Corporation.  All rights reserved.
Starting agent …….. started.

You may come across times when OMS doens’t go down very well. Have a look at Log files for error & kill oms processess. It worked for me
[oracle]$ $OMS_HOME/bin/emctl stop oms
Oracle Enterprise Manager 11g Release 1 Grid Control
Copyright (c) 1996, 2010 Oracle Corporation.  All rights reserved.
Stopping WebTier…
WebTier Successfully Stopped
Stopping Oracle Management Server…
Error Occurred: Error during stop oms. Please check error and log files
[oracle]$ ps -ef | grep oms | cut -d: -f1
oracle   31007     1  0 15
oracle   31893 31847 30 15
[oracle]$ kill -9 31007  31893
[oracle]$ $OMS_HOME/bin/emctl start oms
Oracle Enterprise Manager 11g Release 1 Grid Control
Copyright (c) 1996, 2010 Oracle Corporation.  All rights reserved.
Starting WebTier…
WebTier Successfully Started
Starting Oracle Management Server…
Oracle Management Server Successfully Started
Oracle Management Server is Up

Understanding the 11g Grid Directory Structure , Config & Log files 

$cd /opt/app/oracle/Middleware
[oracle@Middleware]$ tree -L 2
.
|-- WebLogicServer
|   |-- Oracle_WT
|   |-- agent11g
|   |-- domain-registry.xml
|   |-- logs
|   |-- modules
|   |-- oms11g ($OMS_HOME)
|  |-- cfgtoollogs (Install Log)
|   |-- oui
|    |-- installActions2011XXX.log
|    |-- oraInstall2011XXX.log
|  |-- sysman
|   |-- log
|    |-- emrepocminst.log
|   |-- schemamanager
|    |-- emschema.log (Install Log)
|   |-- oracle_common
|   |-- patch_wls1032
|   |-- registry.dat
|   |-- registry.xml
|   |-- user_projects
|   |-- utils
|   |-- wlserver_10.3
|  |-- common
|   |-- emnodemanager (Oracle WebLogic Server Logs)
|    |-- nodemanager.log
|    |-- nodemanager.properties
|
-- gc_inst (EM INSTANCE BASE)
    |-- WebTierIH1
    |   |-- OHS
    |   |-- auditlogs
    |   |-- bin
    |   |-- config
    |   |-- diagnostics
    |       |-- logs
    |           |-- OPMN
    |               |-- opmn  (WebTier logs)
    |                |-- provision.log
    |                |-- opmn.out
    |                |-- debug.log
    |                |-- opmn.log
    |           |-- OHS
    |               |-- ohs1  (WebTier logs)
    |                |-- access_log
    |                |-- mod_wl_ohs.log
    |-- em
    |   |-- EMGC_OMS1 (OMS_NAME)
    |       |-- Sysman
    |           |-- Log
    |               |-- emoms.log : Main log file for the OMS.
 |     |  Number of files created will be = (log4j.appender.emlogAppender.MaxBackupIndex + 1)
 |    |-- emoms.trc : Main trace file for the OMS.
 |    |  Number of files created will be = (log4j.appender.emtrcAppender.MaxBackupIndex + 1)
 |    |-- secure.log
 |    |  Contains output from the 'emctl secure oms' commands.
 |    |-- emctl.msg
 |    |  Created / written to by the HealthMonitor thread of the OMS, when it re-starts the OMS due to a critical error.
 |    |-- emctl.log
 |      Created by the emctl utility, when any commands are executed in the OMS home
    |-- user_projects
        |-- domains
   |-- GCDomain
    |-- servers
     |-- EMGC_OMS1 (Oracle WebLogic Server Logs : GRID Logs)
      |-- logs
       |-- EMGC_OMS1.log  - JVM Application Log
       |-- access.log     - Smiilar to http acess_log
       |-- EMGC_OMS1.out
     |-- EMGC_ADMINSERVER  (Oracle WebLogic Server Logs : AdminServer Logs)
      |-- logs
       |-- EMGC_ADMINSERVER.log
       |-- GCDomain.log
       |-- EMGC_ADMINSERVER.out

---------------------------------------------------------------------------------------------------------
Component         Location
---------------------------------------------------------------------------------------------------------
Oracle HTTP Server (OHS)    <EM_INSTANCE_BASE>/<webtier_instance_name>/diagnostics/logs/OHS/<ohs_name>
For example,    /u01/app/Oracle/gc_inst/WebTierIH1/diagnostics/logs/OHS/ohs1

OPMN      <EM_INSTANCE_BASE>/<webtier_instance_name>/diagnostics/logs/OPMN/<opmn_name>
For example,    /u01/app/Oracle/gc_inst/WebTierIH1/diagnostics/logs/OPMN/opmn1

Oracle WebLogic    <EM_INSTANCE_BASE>/user_projects/domains/<domain_name>/servers/<SERVER_NAME>/logs/<SERVER_NAME>.out
For example,    /u01/app/Oracle/gc_inst/user_projects/domains/GCDomain/servers/EMGC_OMS1/logs/EMGC_OMS1.out