Dear Barath,
Please attach a full screen screen shot from RZ20 to see what is the actual situation
What kind of agent is used? Is this system ABAP or double stack ?
Please check agent log in RZ21:
-Working Directory and Log Files of the CCMS Agents
http://help.sap.com/saphelp_nw70/helpdata/en/c9/aa1a0668720f43adadf91bff1d3c35/frameset.htm
-(CCMS) CCMS Monitoring Infrastructure
http://wiki.scn.sap.com/wiki/display/TechTSG/%28CCMS%29+CCMS+Monitoring+Infrastructure
I would like to ask you to have a look at in SAP notes and blogpost:
#1614214 - RZ20 display does not work after SP upgrade
#522453 - RZ20: Monitoring operating system data
http://scn.sap.com/community/netweaver-administrator/blog/2014/02/05/alerts-in-rz20
Is the SHM segment available?
"Alerts are stored in the shared memory segment and the total number of alerts are restricted based on the segment size and also based on the number of alerts which are kept for each MTE-attribute monitoring node."
Kind regards,
Tamas Istenes SAP Support Engineer
AGS Primary Support, Global Support Center
Please visit : http://scn.sap.com/