ERROR-Agent is blocked. Blocked reason is: Agent is out-of-sync with repository

Communication: Agent to OMS Communication Fails if the Agent is Blocked and Re-synchronization is not Successful [ID 1054605.1]

Enterprise Manager Grid Control - Version: 10.2.0.5 to 10.2.0.5 - Release: 10.2 to 10.2
Information in this document applies to any platform.

Symptoms

After upgrading the OMS and Agent to 10.2.0.5 version, getting the following error in <>/sysman/log/emagent.trc:

Did not receive valid response to ping "ERROR-Agent is blocked. Blocked reason is: Agent is out-of-sync with repository. This most likely means that the agent was reinstalled or recovered. Please contact an EM administrator to unblock the agent by performing an agent resync from the console. Please contact EM adminstrator to unblock the agent"

Cause

The Agent is blocked in the Grid Console due to the "clean-start procedure" followed on the Agent side which included deletion of the <>/sysman/emd/agntstmp.txt.
Re-synchronization of the Agent from Console should help in resumption of the communication. But as per the error from the re-synchronization has failed due to "ORA-20206: Target does not exist: agentmachine.domain:host"

It was found that the <>/sysman/emd/targets.xml file on the Agent host did not have the 'Target TYPE' of 'host' in it. The cause for the missing 'host' entry is not clear.


Note: Although it is not normally advisable to edit the targets.xml file directly, this is an exception.
To correct this problem, follow these steps:

1. Stop the Agent

cd <<AGENT_HOME>>/bin
emctl stop agent

2. Take a backup of the <<AGENT_HOME>>/sysman/emd/targets/xml.
    Edit the file and add the following line:

...
  <Target TYPE="host" NAME="agentmachine.domain"/>
</Targets>

  To identify the agent hostname, open the <<AGENT_HOME>>/sysman/config/emd.properties file and check the parameter EMD_URL. For example:

EMD_URL=https://agenthostname.domain:1830/emd/main/

The hostname of the Agent machine in this case is the agenthostname.domain.

3. Start the Agent

cd <<AGENT_HOME>>/bin
emctl start agent

4. In the Grid Console, Navigate to Setup -> Agents -> click on the Agent name.

5. In the Agent home page, click on the link for 'Resynchronize Agent'
Choose the 'Unblock Agent' option and click Continue