Understanding and controlling crash recovery
Crash recovery is the PostgreSQL subsystem that saves us should the server crash or fail as part of a system crash.
It’s good to understand a little about it and what we can do to control it in our favor.
How to do it…
If PostgreSQL crashes, there will be a message in the server log with the severity level set to PANIC. PostgreSQL will immediately restart and attempt to recover using the transaction log or the WAL.
The WAL consists of a series of files written to the pg_wal subdirectory of the PostgreSQL data directory. Each change made to the database is recorded first in WAL, hence the name write-ahead log, which is a synonym for a transaction log. Note that the former is probably more accurate, since, in the WAL, there are also changes not related to transactions. When a transaction commits, the default (and safe) behavior is to force the WAL records to disk. Should PostgreSQL crash, the WAL will be replayed...
