Whether to use notification or a replication interval to replicate across a site link is configured site link. If all your sites are in the same site link configuration is simple, but if you have several sites links, in a hub-spoke topology e.g., you will have to configure each site link.
You can make the change using any tool able to write to Active Directory attributes. I will use Active Directory Sites and Services since that is the easiest way. The change itself requires Enterpise Admin level permissions.
- Find the site link you want to change, right click and select Properties.
- Select the Attributes Editor tab.
- Find the options attribute (make sure that you display all attributes regardless of whether they have a value or not, since this attribute does not have a value by default).
- Set the value of the options attribute to 1. Notice how you will now have an explanation behind the 1 value indicating that you have configured the link to use notifications (USE_NOTIFY).
- Replicate this change to all DC manually or wait for regular scheduled Active Directory replication.