Replication is a set of technologies for copying and distributing data and database objects from one database to another and then synchronizing between databases to maintain consistency.

Types of Replication.
1. Snapshot replication
2. Transactional replicaion
3. Merge replication
4. Peer-to-peer replication

Always on : https://youtu.be/eJbe4roH_NE

Clustering : https://youtu.be/IHzynh0CnpI

Mirroring : https://youtu.be/DlukbLQCkZ0

Log Shipping : https://youtu.be/S1SaSJZtYzA