ULN channels are of the following types:

Core

Consists of required channels of a specific Oracle Linux release, including the *_latest channel which distributes the latest possible version of any package release. Registered systems are automatically subscribed to appropriate core channels.

Caution:

Unsubscribing from the _latest channel can make the system vulnerable to security-related issues. We recommend that you keep the system subscribed to this channel.

Base and Patch

Extra ULN channels that are available for various OS update levels or revisions.

You can maintain a system at a specific update by unsubscribing from the _latest channel and replacing it with _base and _patch channels. However, this configuration can leave a system vulnerable to security issues because Oracle stops updating the patch channels after releasing a new update level. Also, software in the _appstream channel is always released in line with the latest release. Fixing the system to a particular update level could create dependency issues when Oracle updates the software in the _appstream channel.

Not all channels are available for all architectures. Use the ULN web interface to check what channels are available for a specific system architecture. See Managing a System's Channel Subscriptions. See also Main ULN Channels.