To check what the timeout is set
em@emap1>./emctl get property -name oracle.sysman.eml.maxInactiveTime Oracle Enterprise Manager Cloud Control 12c Release 2 Copyright (c) 1996, 2012 Oracle Corporation. All rights reserved. SYSMAN password: Value for property oracle.sysman.eml.maxInactiveTime for oms All Management Servers is null null = default of 45 minutesAfter you have checked the value . you can change it
/u01/app/oraem/oem12c/oms/bin em@emap1>./emctl set property -name oracle.sysman.eml.maxInactiveTime -value 90 Oracle Enterprise Manager Cloud Control 12c Release 2 Copyright (c) 1996, 2012 Oracle Corporation. All rights reserved. SYSMAN password: Property oracle.sysman.eml.maxInactiveTime has been set to value 90 for all Management Servers OMS restart is required to reflect the new property valueThis will set the inactive time to 90 minutes . you will need an OMS bounce for this to take effect. Please ensure that whatever value you set meets your requirements and the security requirements of your company