yum Command Hangs on Running Transaction Test Message Error

the yum process is killed manually using the kill command.

This error indicates that other duplicate yum processes running on the system or older yum process causing problem. To fix this problem either reboot the server or type the following commands:
# /bin/rm /var/lib/rpm/__db.*
# cd /var/cache/yum
# /bin/rm -rf *
# yum clean all
# yum update