In the preparation steps for the Satellite 6.2 to Satellite 6.3 there is a mention for what repositories should be enabled. It seems to me there is a mistake in it.
It states:
Ensure only the required repositories are enabled.

subscription-manager repos --disable=*

subscription-manager repos \

--enable=rhel-7-server-rpms \
--enable=rhel-server-rhscl-7-rpms \
--enable=rhel-7-server-satellite-maintenance-6-rpms \
--enable=rhel-7-server-satellite-6.2-rpms

What I think it should be:
Ensure only the required repositories are enabled.

subscription-manager repos --disable=*

subscription-manager repos \

--enable=rhel-7-server-rpms \
--enable=rhel-server-rhscl-7-rpms \
--enable=rhel-7-server-satellite-maintenance-6-rpms \
--enable=rhel-7-server-satellite-6.3-rpms