For more information, see the following section "Switching between Update Modes".Updatable subscriptions for transactional replication allow Subscribers to replicate changes to the Publisher.Msg 3609, Level 16, State 1, Line 1The transaction ended in the trigger. publisher is one which is the primary data which publish data to its subscribers and in your case updates at the subscibe are also results o update on primary.
This feature remains supported in versions of SQL Server from 2012 through 2016.This feature will be removed in a future version of Microsoft SQL Server.Because the updates are propagated asynchronously to the Publisher, the same data may have been updated by the Publisher or by another Subscriber and conflicts can occur when applying the updates.Conflicts are detected and resolved according to a conflict resolution policy that is set when creating the publication.But what is immediate-updating Subscribers (Snapshot)? Merge is more applicable in situations where your subscribers mostly remain disconnected from the publisher.
Whereas, immediate updating subscribers uses Distributed Transaction Coordinator (DTC) which requires that when a subscriber changes data then that update gets applied to publisher immediately.Enable updating subscriptions for transactional publications on the Publication Type page of the New Publication Wizard.To use updating subscriptions, you must also configure options in the New Subscription Wizard.Avoid using this feature in new development work, and plan to modify applications that currently use this feature.When using updatable subscriptions you can specify that a subscription should use one update mode and then switch to the other if the application requires it.When possible, prompt users to enter security credentials at runtime.