Hi Chandhya,
The rollback procedure is explained here
http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/ucmapMigrate/10_5_1/CUCM_BK_M24251C0_00_migrate-procedure-for-cucm_1051/CUCM_BK_M24251C0_00_migrate-procedure-for-cucm_1051_chapter_010.html
HTH
Manish