Log shipping is a replication technique that's used by many database management systems. The master records change in a transaction log (WAL), and then the log data is shipped from the master to the standby, where the log is replayed.
In PostgreSQL, PSR transfers WAL data directly from the master to the standby, giving us integrated security and reduced replication delay.
There are two main ways to set up streaming replication: with or without an additional archive. Setting it up without an external archive is presented here, as it is the simpler and more efficient way. However, there is one downside that suggests that the simpler approach may not be appropriate for larger databases, which is explained later in this recipe.