Database Management · Advanced level

Advanced level · Module 4: Replication, Availability and Recovery · Lesson 1 of 4

Streaming Replication

Copy changes continuously from a primary to standby servers and use replicas for reading.

In this lesson you will

  • Set up a streaming replica
  • Monitor replication lag and use read replicas appropriately

Key concepts

primary and standbywrite-ahead log streamingreplication lagread replica

The lesson

Streaming replication sends the primary's write-ahead log to standby servers, which apply it continuously. A standby can take over if the primary fails, and can serve read-only queries.

Replication lag is how far a standby is behind. Reports run on a replica may miss the latest changes; applications that need to read their own writes immediately should use the primary.

Replication protects against server failure, not mistakes: a DELETE on the primary is replicated too. Backups remain essential.

Step by step

  1. Configure a primary and a standby.
  2. Insert data on the primary and read it on the standby.
  3. Measure replication lag.
  4. Show that a mistaken DELETE is replicated.

Practice activity

Set up a streaming standby for the health database.

Expected result: The standby stays in sync, its lag is monitored and it answers read-only queries.

Check your understanding

  1. Does replication replace backups?

    Show answer

    No; mistakes are replicated too.

  2. What is replication lag?

    Show answer

    How far a standby is behind the primary.

Taught live by an instructor — online or in person. Free course lessons are for self-study and do not lead to a certificate — see registration options.