You can refer this guide for upgrading callmanager 4.x to 6.x
http://cisco.com/en/US/docs/voice_ip_comm/cucm/upgrade/6_0_1/upgrd601.html
The installation process allows you to perform a basic installation, upgrade from Cisco Unified Communications Manager 4.x to Cisco Unified Communications Manager 6.0(1), and upgrade to a newer service release during the installation.