Hi,
Reason codes describe why an agent has changed to the Not Ready agent state or has logged out. Reason codes are set up and maintained using the Reason
Code window.
NOTE: You cannot enable reason codes unless at least one user-defined
reason code exists for Logout and one exists for Not Ready.
Take a look out the below URL for more info,
http://www.cisco.com/univercd/cc/td/doc/product/voice/sw_ap_to/apps_3_5/english/admn_app/cad_admn.pdf
Hope it helps.
Regards
Venkat