Hello ZL
Follow information for your reference
http://scn.sap.com/thread/3232846
http://scn.sap.com/message/14127967
http://scn.sap.com/thread/3300113
http://scn.sap.com/thread/3198283
http://scn.sap.com/thread/3340865
http://wiki.sdn.sap.com/wiki/display/EHP/Overview+SAP+Enhancement+Packages
Hope helpful.
Kind Regards.