"Subscription Concepts and Workflows" outlines the importance of clear, detailed, and consistent subscription tracking. It is an increasingly critical part of IT maintenance. The older channel-based subscription management process in RHN Classic was great at providing access, but it was very difficult to get an accurate accounting of how subscriptions were applied, how many subscriptions were being used, where subscriptions were being used, and what any individual system was using.

As the need for more granular subscription management has emerged, Customer Portal Subscription Management, Subscription Asset Manager, and similar subscription services from Red Hat are designed to focus exclusively on subscription management. Other systems management tasks, such as content delivery and configuration management, are then handled by other applications designed for those system management tasks.

For that reason, Customer Portal Subscription Management or Subscription Asset Manager are used in conjunction with a robust systems management tool such as Satellite 6, JBoss Operations Network, Puppet, and other applications.

Red Hat Enterprise Linux systems should be migrated to Customer Portal Subscription Management or Subscription Asset Manager in order to provide the enhanced subscription tracking, asset inventory management, and compliance reporting that a robust subscription management service offers. Customer Portal Subscription Management offers better and more detailed subscription information which is invaluable to IT administrators.

The core of Customer Portal Subscription Management is defining a relationship between subscriptions and the systems which are using them. To achieve this, subscriptions are organized based on the available and installed products for a system.

As the terms imply, subscriptions in Customer Portal Subscription Management define available products. These are the products a system is covered to install and update and receive support for. Locally, Red Hat Subscription Manager tracks what products are actually installed and provides information on how the installed, real products match against the potential or attached subscriptions.

Customer Portal Subscription Management has a very narrow focus. It only concerns subscriptions and products. Therefore, it only manages subscriptions and content delivery. Higher level system management is performed by system management products like Satellite 6 or JBoss Operations Network,

RHN Classic is more focused on general system management than on subscription management alone. (In this way, it is a hosted version of Satellite.)

RHN Classic provides a number of tools to manage systems, including configuration file editing and kickstarting new systems. Part of that management is registering the system and assigning subscriptions, but with an important difference from Customer Portal Subscription Management. RHN Classic tries to provide access to subscribed content, so the intent is not to track usage but to make sure that access is available.

The simplest way to accomplish this is to organize all products into pools or channels, and then use subscriptions to provide access to those channels. This results in a much simpler global view of subscriptions, but it loses the relationship between local systems, subscriptions, and installed products.

Both Customer Portal Subscription Management and Subscription Asset Manager are exclusively focused on subscription management. They are not, and are not intended to be, systems management tools. This is different than RHN Classic, which included subscription management as part of its overall purpose of systems management.

Because of the different emphases in Customer Portal Subscription Management and RHN Classic, there are differences in what functionality they support.

One side effect of the different emphases in Customer Portal Subscription Management and RHN Classic is how they handle the subscription and registration processes.

In RHN Classic, which emphasizes access, systems are automatically subscribed to compatible channels as part of its registration process. Registration itself is the act of granting access.

Customer Portal Subscription Management is dedicated to defining relationships between purchased subscriptions and real product usage. While it is possible to attach compatible subscriptions automatically to a system (and this is the default configuration for firstboot), it is also possible to attach subscriptions manually. This gives administrators the option of exerting greater control over what subscriptions are attached and when — and even the option to force subscriptions when they are not otherwise compatible with a system.

A system should be registered with either Customer Portal Subscription Management (the default) or with RHN Classic — it cannot be registered with both. The two subscription services are mutually exclusive, with separate sets of client tools and separate system inventories.

When a system is registered with either system, it is given an identifier for that subscription inventory. Both Customer Portal Subscription Management and RHN Classic check for a pre-existing identifier before completing the registration process.

If a system is already registered with one system, then attempting to register with the other results in an error.

The migration process involves moving the system's full registration information — including its subscriptions — from RHN Classic to Customer Portal Subscription Management. The system is identified by a unique number. This can either be a systemid value (Red Hat Enterprise Linux 5 or 6) or an installation number (Red Hat Enterprise Linux 5).

The migration script takes the identifier and then uses it to extract and migrate the system entry. rhn-migrate-classic-to-rhsm performs the migration based on the system ID, in the /etc/sysconfig/rhn/systemid file.