Existing lock /var/run/yum.pid: another copy is running as pid .
Another app is currently holding the yum lock; waiting for it to exit...
The other application is: yum-cron
Memory : 23 M *** (418 MB ***)
Started: Wed Apr 29 2020 - 12:41 ago
State : Sleeping, pid:

Solution:

$ yum list

[root@user bin]# yum list
Failed to set locale, defaulting to C
Existing lock /var/run/yum.pid: another copy is running as pid .
Another app is currently holding the yum lock; waiting for it to exit...
The other application is: yum-cron
Memory : 23 M *** (418 MB ***)
Started: Wed Apr 29 2020 - 13:21 ago
State : Sleeping, pid:

Identify the PID from the above output.
State : Sleeping, pid:

Now, Kill if it is a stale process to resolve this issue.
$ kill -9