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When installing Enterprise Manager 12c, the host value can come from a number of places for different applications/tiers. For most, it comes from the environment variable $ORACLE_HOSTNAME, (for Windows Servers, %ORACLE_HOSTNAME%).
The OHS1 target, aka Oracle Apache in the middle tier of the EM12c environment pulls it’s value from the etc/hosts file, (for Unix as well as Windows) and so it is vulnerable with a virtual host name or host name change occurs. It can, however, be updated post installation when the OHS1 target fails to return an active status in the EM12c console.
The file that control the configuration of the OHS1 target is the topology.xml file that is located in the $OMS_HOME\user_projects\domains\GCDomain\opmn\topology.xml
Edit the topology.xml file and replace/add the following entries in bolded text, replacing Virtual_Cluster_name with the name of the Cluster:– <ias-instance id=”instance1″ oracle-home=”G:\app\aime\product\em12c\Oracle_WT” instance-home=”G:\app\aime\product\gc_inst\WebTierIH1″ host=”<New Host Name>” port=”6701″> – <ias-component id=”ohs1″ type=”OHS” mbean-class-name=”oracle.ohs.OHSGlobalConfig” mbean-interface-name=”oracle.ohs.OHSGlobalConfigMXBean” port=”9999″ host=”<New Host Name>“>
Save the file with the new changes.
Log into your EM12c console as the SYSMAN user, (or another user with appropriate privileges) and click on All Targets. Either do a search for the OHS1 target or just scan down and double-click on it. The target will show as down and display the incorrect associated targets with the HTTP Server:
You will need to remove and re-add the target to have the EM12c utilize the topology.xml file configuration update to the new host name.
To do this, click on Oracle HTTP Server–> Target Setup –> Remove Target. The target for the Oracle Apache server/HTTP Server, along with its dependents have now been removed.
To re-add the OHS1 target, we are going to use a job already built into EM12c. Go back to All Targets the Targets drop down. At the very top you will commonly see the EMGC_GCDomain, (Grid Control Domain, yes, it’s still referred to it as that… :)) Log into this target. There are two “levels” to this target, the parent and then the farm. Either one will offer you a job in the drop down to Refresh Weblogic Domain.
Once you click on this job, it will ask you to remove or add targets. You can simply choose to Add Targets and the job will first search for any missing targets that need to be re-added. Commonly it will locate 12 and display a list of the targets it wishes to add. You will note that the OHS1 target now displays the CORRECT host name.
Close the window and choose to complete through the wizard steps to add these targets to the Weblogic domain.
Return to All Targets and access the OHS1 Target to verify that it now displays an active status- it may take up to one collection to update the target status.