Atomic Replace - overwrites existing configuration with imported configuration data. Any objects in the existing configuration that do not exist in the imported configuration are deleted. Objects are deleted from the existing configuration that have children in the existing configuration but do not have children in the incoming imported configuration. For example, if an existing configuration has two tenants, solar and wind, but the imported backed up configuration was saved before the tenant wind was created, tenant soar is restored from the backup but tenant wind is deleted.
Rollback is when a previous configuration snapshot is used to replace the current APIC configuration. This can be done on the granularity of a snapshot file. This means that a single tenant can be moved back to a previous configuration while the other tenants keep their current configuration state. This is often referred to as partial rollback. When all of the configuration files for a particular version are used to replace the current APIC configuration, this is referred to as a full rollback.