if you face this error "Operation Failed, Unable to start iomgr" while attempting to start or stop ArcSDE service. There is high probablity that you have orphan processes in your server.
for example,
if you are hosting your ArcSDE engine on a Unix server.
use the following command:
ps -ef | grep gsrvr
it will list the orphan sde process. you need to kill them using the "kill" command.
