rpm and yum commands are not working+ linux

At the time of patching I encountered a error and I wanted to check the version of yum on TEM server and the server which is going to patched. 

But found that neither the rpm or yum commands are working & session was getting hang.

#yum info yum or # rpm -qa |grep -i yum

session was hanging

 In such case, check whether any lock is created under  /var/lib/rpm/ & if it is there remove it because these locks are creating problem while running rpm commands.

1. # ls -lrt /var/lib/rpm/__db.*

-rw-------  1 root root   753664 Dec  9 07:05 __db.004

-rw-------  1 root root  1318912 Dec  9 07:05 __db.003

-rw-------  1 root root    24576 Dec  9 09:02 __db.001

-rw-------  1 root root   237568 Dec  9 09:05 __db.002

2. # rm /var/lib/rpm/__db.*

3. # ls -lrt /var/lib/rpm/__db.*

4. rpm commands and yum commands will run now.

Thanks,

Kiran Jadhav