Oracle Enterprise Manager has a very extensive, comprehensive and flexible procedures which enables the users to have a very smooth process in patching of the targets monitored by the EM.

Enterprise Manager Patching ensures the vulnerabilities of the targets are removed on time and critical/security fixes are applied appropriately.

More information about the Patching and it Automation can be found here:
On OTN - http://www.oracle.com/technology/products/oem/mgmt_solutions/provisioning.html
Critical Patch Updates - http://www.oracle.com/technology/deploy/security/alerts.htm