Does PostgreSQL Automatically Rotate WAL Files if archive_mode is Off?

archive-logpostgresqlpostgresql-9.6transaction-log

I'm relatively new to PostgreSQL administration and I'm attempting to pick up the nitty gritty details as I go. My question is, assuming I have no need for disaster recovery and I don't turn on archiving by setting up archive_mode = on, does Postgres have an internal mechanism to rotate WAL files out of pg_xlog? if so, what is the frequency?

On a slightly different note, what is the impact of setting archive_mode = on but not configuring an archive_command – is there a default location Postgres will attempt to archive to?

Best Answer

If archive_mode = off, PostgreSQL will delete old WAL files as soon as they are older than the latest checkpoint. These checkpoints occur by default at least every 5 minutes, so there should never be many old WAL files around.

If you set archive_mode = on, a WAL file are only deleted once archive_command has returned success for that file. An empty archive_command should always do that immediately. It is a tradition to set archive_command = '/bin/true' to indicate that you temporarily disabled archiving.

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