Multitenant Applications and the process of upgrading:

This is a continuation of the articles on multitenancy with the most recent one linked MultitenantApplicationsPart84.docx. This article focuses on synchronizing data between publishers and subscribers in a multitenant deployment.

Synchronization can occur in the following ways: 1) continuously, which is typical for transactional replication, 2) On demand, which is typical for merge replication. And 3) On a schedule, which is typical for snapshot replication. Replication happens by way of state or operations transfer which is like the well-known log shipping and mirroring options. State gets overwritten on the destinations whereas operations are re-executed on the destination.

When a subscription is synchronized, different processes occur based on the different types of replication. Snapshot synchronization is one where the Distribution Agent reapplies the snapshot at the Subscriber so that schema and data at the subscription database is consistent with the publication database. Modifications to data or schema when made at the publisher, require a new snapshot to be generated in order to be propagated. Transactional replication is one where the distribution agent transfers, updates, inserts, deletes and any other change from the distribution database to the subscriber. Merge replication is one where the merge agent uploads the changes from the subscriber to publisher and then downloads changes from the publisher to the subscriber. Conflicts are detected and resolved. Data is converged and the publisher and all subscribers eventually end up with the same data values. If conflicts were detected and resolved, work that was committed by some of the users is changed to resolve the conflict according to defined policies

Synchronizing a push subscription can be done on demand by connecting the source such as a publisher, a subscriber, or a monitor agent in the middle, to a tool that that can initiate the synchronization to the destination. Status of the synchronization is usually displayed and will show completed when done. A pull synchronization only happens from the subscriber side.

Synchronization can also be scheduled by defining a synchronization schedule that controls the replication agent will run. Distribution agents and merge agents can run continuously, run on demand and run on a schedule.

Reference: https://1drv.ms/w/s!Ashlm-Nw-wnWhLMfc6pdJbQZ6XiPWA?e=fBoKcN