Offline security update - No Packages marked for Update

Hey,

I am trying to perform security updates on an offline RHEL (6.9) system (as described in https://access.redhat.com/solutions/45956). However, when performing the final step and calling yum update, it returns:

"There was an error communicating with RHN.
RHN Satellite or RHN Classic support will be disabled.
rhn-plugin: Error communicating with server. The message was:
Temporary failure in name resolution
Setting up Update Process
No Packages marked for Update"

I have found I need to disable the rhn plugin as it tries to talk to the internet when a yum function is called otherwise.

However, yum update now returns:

"Loaded plugins: kernel-rt-protect, product-id, search-disabled-repos, security, subscription-
: manager
Setting up Update Process
No Packages marked for Update"

Solutions for the "No Packages marked for Update" problem (https://access.redhat.com/solutions/33050, https://kadirsert.blogspot.co.uk/2012/03/no-packages-marked-for-update-returns.html) state that this is due to the rhn plugin being disabled, but as before it cannot be enabled to the lack of an internet connection.

Does anyone know a solution to this?

Thanks a lot!