How to Disable Inactivity Log Out in Enterprise Manager Cloud Control 12c

/app/oracle/Middleware/oms/sysman/config

Add the following line after the last line in the above file

oracle.sysman.eml.maxInactiveTime=1440

Restart your OMS using below commands

$OMS_HOME/bin/emctl stop oms

$OMS_HOME/bin/emctl start oms