EM12c - How to take oms logs in debug mode?

Run below command on OMS to activate debug log and collect emoms.log/trc.

Fetch the current setting of logging by running below command
%<middleware_home>/oms/bin/emctl get property -sysman_pwd  <repos user psswd> -name log4j.logger.oracle.sysman
Oracle Enterprise Manager Cloud Control 12c Release 12.1.0.1.0 
Copyright (c) 1996, 2012 Oracle Corporation.  All rights reserved.
Value for property log4j.logger.oracle.sysman for oms <hostname>:<port>_Management_Service is null


Then set the log level to debug
%<middleware_home>/oms/bin/emctl set property -sysman_pwd  <repos user psswd> -name log4j.logger.oracle.sysman -value DEBUG -module logging
Oracle Enterprise Manager Cloud Control 12c Release 12.1.0.1.0 
Copyright (c) 1996, 2012 Oracle Corporation.  All rights reserved.
Property log4j.logger.oracle.sysman for oms <hostname>:<port>_Management_Service has been set to value DEBUG
OMS restart is not required to reflect the new property value

After enabling OMS java debug log, visit required EM pages
Take the OMS logs i.e. EMGC_OMS1.out, emoms.log and emoms.trc etc.