Why does yum return error: [Errno 256] No more mirrors to try ?

https://access.redhat.com/solutions/203603

ISSUE

yum update fails with the error : [Errno 256] No more mirrors to try
yum update fails with :-
Error Downloading Packages:
InstallMedia: [Errno 256] No more mirrors to try.
yum fails with :
Error Downloading Packages:
ftp-0.17-35.el5.x86_64:failure:ftp-0.17-35.el5.x86_64.rpm from Red5repo55:[Errno 256] No more mirrors to try. [[6]]" (code -1) Packages Scheduled
yum fails with :
Downloading Packages:
https://cdn.redhat.com/content/dist/rhel/server/6/6Server/x86_64/supplementary/os/Packages/java-1.6.0-ibm-1.6.0.15.0-1jpp.1.el6_4.x86_64.rpm: [Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 Not Found"
Trying other mirror.
Error Downloading Packages:
1:java-1.6.0-ibm-1.6.0.15.0-1jpp.1.el6_4.x86_64: failure: Packages/java-1.6.0-ibm-1.6.0.15.0-1jpp.1.el6_4.x86_64.rpm from rhel-6-server-supplementary-rpms: [Errno 256] No more mirrors to try.
ENVIRONMENT

Red Hat Enterprise Linux 5 and later
Red Hat Network (RHN)
Subscription Management (RHSM)
RESOLUTION

Check what files are present under /etc/yum.repos.d directory by:-
# ll /etc/yum.repos.d
If the system is registered to RHN Classic, only rhel-source.repo should be present under /etc/yum.repos.d/.
If the system is registered to subscription-manager (RHSM), rhel-source.repo and 'redhat.repo' are present.
If any local repositories, or any other media repositories are present, remove them by :-
# rm -rf /etc/yum.repos.d/<local or other repository name>
Remove old yum cache from system by running following commands:
# rm -fr /var/cache/yum/*
# yum clean all
Check if you can list the valid repositories by :-
# yum repolist
ROOT CAUSE

This issue persist due to following reasons:
Corrupted yum cache.
Inaccessibility of a repository URL from the system.
Presence of customized or other media repositories.
DIAGNOSTIC STEPS

Check the accessibility of the repository URL in the system/network.
# ping URL
Check the repositories under /etc/yum.repos.d
ll /etc/yum.repos.d
Collect a sosreport of the affected system.