What is replication in SQL?

Replication in SQL is the process of copying data from one database server to another.

It's used to:

• improve reliability, if the primary server fails, the data survives on the copy;
• spread the load, the primary server handles writes, while the copies (replicas) handle read requests;
• speed up access, users in different regions can reach the nearest replica.

There are usually two types:

• Synchronous replication, changes get written to the replica immediately (slower, but safer).
• Asynchronous replication, data is saved on the primary server first and then copied to the replica (faster, but with a possible delay).

Replication helps a database run faster, more reliably, and more safely.