Oracle Grid Control Agent configuration/communication problem.

If your suddenly get following errors in Grid Control console:

If trying to configure database error will appear:
"Error occurred while getting information for the specified target. Possible reasons include: the target doesn't exist; connection to the target failed."

If trying to configure agent this error will appear:
"Communication between the Oracle Management Service host to the Agent host is unavailable. Any functions or displayed information requiring this communication link will be unavailable. For example: deleting/configuring/adding targets, uploading metric data, or displaying Agent home page information such as Agent to Management Service Response Time (ms)."

And when going into database page in grid control following error:
"java.lang.Exception: java.io.IOException: javax.net.ssl.SSLPeerUnverifiedException: peer not authenticated"


These are coming because of some kind network connectivity issues with secured agents.

Workaround for these errors is:

Check oms detailed status (this asks SYSMAN password)
$OMS_HOME/bin/emctl status oms -details

If Agent upload and OMS Console is locked then run following:
(To remove the restriction for HTTPS uploads from the Management Agents, repeat the preceding procedure, but replace the emctl secure lock command with the following command: (this asks SYSMAN and agent securing password.)
$OMS_HOME/bin/emctl secure unlock 

$OMS_HOME/bin/emctl stop oms -all
$OMS_HOME/bin/emctl start oms
 
After unlock run following for each of problematic Grid Control Agents:
$AGENT_HOME/bin/emctl unsecure agent
$AGENT_HOME/bin/emctl upload agent
$AGENT_HOME/bin/emctl status agent

 After this errors are gone. 



If want to use secure OMS and Agents try to find problem of HTTPS connections between your OMS server and Agent servers. And after that run : 
$OMS_HOME/bin/emctl secure lock 

$OMS_HOME/bin/emctl stop oms -all
$OMS_HOME/bin/emctl start oms

And then secure agents with:
$AGENT_HOME/bin/emctl secure agent
$AGENT_HOME/bin/emctl upload agent
$AGENT_HOME/bin/emctl status agent

 
Sometimes simple unsecure and secure can fix the problem.