To tentativelly recover from a plugin deployment that failed on either of the Management Servers, for example in the latest step ‘Starting Management Server’, leaving the deployment unfinished and leaving the status as ‘deploying’ in the OMS UI, a possible solution is to start a dummy pluginca session on this OMS server where the session could not complete.
To example, to recover from an issue deploying the ZFS plugin agent, that occured on the second OMS:
On the second OMS server:
$ORACLE_HOME/bin/pluginca -plugins oracle.sun.oss7=126.96.36.199.0 -action all -isfirstoms false
This session would display in success status, on the deployment activity page for this plugin. The old session stuck in status ‘deploying’ will then be ignored.