OEM 12c R3 has a very useful Perl script which allows removing an installed OEM agent in the host. The process is quite straightforward just by invoking the AgentDeinstall.pl script located under:
$AGENT_HOME/sysman/install/AgentDeinstall.pl
[oracle@ol6-112 12.1.0.3.0]$ /u01/app/oracle/agent12cr3/core/12.1.0.3.0/perl/bin/perl /u01/app/oracle/agent12cr3/core/12.1.0.3.0/sysman/install/AgentDeinstall.pl -agentHome $AGENT_HOME
Agent Oracle Home: /u01/app/oracle/agent12cr3/core/12.1.0.3.0
NOTE: The agent base directory: /u01/app/oracle/agent12cr3 will be removed after successful deinstallation of agent home.
DetachHome Command executed:/u01/app/oracle/agent12cr3/core/12.1.0.3.0/oui/bin/runInstaller -detachHome -force -depHomesOnly -silent ORACLE_HOME=/u01/app/oracle/agent12cr3/core/12.1.0.3.0 -waitForCompletion -invPtrLoc /u01/app/oracle/agent12cr3/core/12.1.0.3.0/oraInst.loc
Starting Oracle Universal Installer...
Checking swap space: must be greater than 500 MB. Actual 8015 MB Passed
The inventory pointer is located at /u01/app/oracle/agent12cr3/core/12.1.0.3.0/oraInst.loc
'DetachHome' was successful.
Starting Oracle Universal Installer...
Checking swap space: must be greater than 500 MB. Actual 8015 MB Passed
The inventory pointer is located at /u01/app/oracle/agent12cr3/core/12.1.0.3.0/oraInst.loc
The Oracle home '/u01/app/oracle/agent12cr3/sbin' could not be updated as it does not exist.
Deinstall Command executed:/u01/app/oracle/agent12cr3/core/12.1.0.3.0/oui/bin/runInstaller -deinstall -silent "REMOVE_HOMES={/u01/app/oracle/agent12cr3/core/12.1.0.3.0}" -waitForCompletion -removeAllFiles -invPtrLoc /u01/app/oracle/agent12cr3/core/12.1.0.3.0/oraInst.loc
Starting Oracle Universal Installer...
Checking swap space: must be greater than 500 MB. Actual 8015 MB Passed
Preparing to launch Oracle Universal Installer from /tmp/OraInstall2013-11-11_02-22-46PM. Please wait ...Oracle Universal Installer, Version 11.1.0.11.0 Production
Copyright (C) 1999, 2013, Oracle. All rights reserved.
Starting deinstall
Deinstall in progress (Monday, November 11, 2013 2:23:00 PM CST)
Configuration assistant "Agent Deinstall Assistant" succeeded
............................................................... 100% Done.
Deinstall successful
End of install phases.(Monday, November 11, 2013 2:23:37 PM CST)
End of deinstallations
Please check '/u01/app/oraInventory/logs/silentInstall2013-11-11_02-22-46PM.log' for more details.
Do you want us to delete the old oracle home [yes/no] :y
Hope this help you when need to remove an OEM agent installation.
Thanks,
Alfredo