Write-Ahead Log
Dossier URLs remain flat; this category exists only to organize browsing and the sidebar.
archive_cleanup_command
archive_cleanup_command sets the shell command that will be executed at every restart point. It is a sighup setting present in PG12–18; the latest recorded boot default is empty.
archive_command
archive_command — Sets the shell command that will be called to archive a WAL file. Observed in PG9.0–19 Beta 3; its last measured boot default is empty string in PG19 Beta 3, with sighup context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
archive_library
archive_library sets the library that will be called to archive a WAL file. It is a sighup setting present in PG15–18; the latest recorded boot default is empty.
archive_mode
archive_mode — Allows archiving of WAL files using “archive_command”. Observed in PG9.0–19 Beta 3; its last measured boot default is off in PG19 Beta 3, with postmaster context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
archive_timeout
archive_timeout — Sets the amount of time to wait before forcing a switch to the next WAL file. Observed in PG9.0–19 Beta 3; its last measured boot default is 0 s in PG19 Beta 3, with sighup context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
checkpoint_completion_target
checkpoint_completion_target — Time spent flushing dirty buffers during checkpoint, as fraction of checkpoint interval. Observed in PG9.0–19 Beta 3; its last measured boot default is 0.9 in PG19 Beta 3, with sighup context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
checkpoint_flush_after
checkpoint_flush_after — Number of pages after which previously performed writes are flushed to disk. Observed in PG9.6–19 Beta 3; its last measured boot default is 256 KiB (32 × 8kB) in PG19 Beta 3, with sighup context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
checkpoint_segments
checkpoint_segments — Sets the maximum distance in log segments between automatic WAL checkpoints. Observed in PG9.0–9.4; its last measured boot default is 3 in PG9.4, with sighup context. It was removed in PG9.5.
checkpoint_timeout
checkpoint_timeout — Sets the maximum time between automatic WAL checkpoints. Observed in PG9.0–19 Beta 3; its last measured boot default is 5 min in PG19 Beta 3, with sighup context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
checkpoint_warning
checkpoint_warning — Sets the maximum time before warning if checkpoints triggered by WAL volume happen too frequently. Observed in PG9.0–19 Beta 3; its last measured boot default is 30 s in PG19 Beta 3, with sighup context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
commit_delay
commit_delay — Sets the delay in microseconds between transaction commit and flushing WAL to disk. Observed in PG9.0–19 Beta 3; its last measured boot default is 0 in PG19 Beta 3, with superuser context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
commit_siblings
commit_siblings — Sets the minimum number of concurrent open transactions required before performing “commit_delay”. Observed in PG9.0–19 Beta 3; its last measured boot default is 5 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
fsync
fsync — Forces synchronization of updates to disk. Observed in PG9.0–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with sighup context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
full_page_writes
full_page_writes — Writes full pages to WAL when first modified after a checkpoint. Observed in PG9.0–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with sighup context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
max_wal_size
max_wal_size — Sets the WAL size that triggers a checkpoint. Observed in PG9.5–19 Beta 3; its last measured boot default is 1 GiB in PG19 Beta 3, with sighup context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
min_wal_size
min_wal_size — Sets the minimum size to shrink the WAL to. Observed in PG9.5–19 Beta 3; its last measured boot default is 80 MiB in PG19 Beta 3, with sighup context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
recovery_end_command
recovery_end_command sets the shell command that will be executed once at the end of recovery. It is a sighup setting present in PG12–18; the latest recorded boot default is empty.
recovery_prefetch
recovery_prefetch prefetches referenced blocks during recovery. It is a sighup setting present in PG15–18; the latest recorded boot default is try.
recovery_target
recovery_target can be set to “immediate” to end recovery as soon as a consistent state is reached. It is a postmaster setting present in PG12–18; the latest recorded boot default is empty.
recovery_target_action
recovery_target_action sets the action to perform upon reaching the recovery target. It is a postmaster setting present in PG12–18; the latest recorded boot default is pause.
recovery_target_inclusive
recovery_target_inclusive sets whether to include or exclude transaction with recovery target. It is a postmaster setting present in PG12–18; the latest recorded boot default is on.
recovery_target_lsn
recovery_target_lsn sets the LSN of the write-ahead log location up to which recovery will proceed. It is a postmaster setting present in PG12–18; the latest recorded boot default is empty.
recovery_target_name
recovery_target_name sets the named restore point up to which recovery will proceed. It is a postmaster setting present in PG12–18; the latest recorded boot default is empty.
recovery_target_time
recovery_target_time sets the time stamp up to which recovery will proceed. It is a postmaster setting present in PG12–18; the latest recorded boot default is empty.
recovery_target_timeline
recovery_target_timeline specifies the timeline to recover into. It is a postmaster setting present in PG12–18; the latest recorded boot default is latest.
recovery_target_xid
recovery_target_xid sets the transaction ID up to which recovery will proceed. It is a postmaster setting present in PG12–18; the latest recorded boot default is empty.
restore_command
restore_command sets the shell command that will be called to retrieve an archived WAL file. It is a sighup setting present in PG12–18; the latest recorded boot default is empty.
summarize_wal
summarize_wal starts the WAL summarizer process to enable incremental backup. It is a sighup setting present in PG17–18; the latest recorded boot default is off.
synchronous_commit
synchronous_commit — Sets the current transaction’s synchronization level. Observed in PG9.0–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
wal_buffers
wal_buffers — Sets the number of disk-page buffers in shared memory for WAL. Observed in PG9.0–19 Beta 3; its last measured boot default is -1 8kB in PG19 Beta 3, with postmaster context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
wal_compression
wal_compression — Compresses full-page writes written in WAL file with specified method. Observed in PG9.5–19 Beta 3; its last measured boot default is off in PG19 Beta 3, with superuser context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
wal_decode_buffer_size
wal_decode_buffer_size sets the buffer size for reading ahead in the WAL during recovery. It is a postmaster setting present in PG15–18; the latest recorded boot default is 512 KiB.
wal_init_zero
wal_init_zero writes zeroes to new WAL files before first use. It is a superuser setting present in PG12–18; the latest recorded boot default is on.
wal_level
wal_level — Sets the level of information written to the WAL. Observed in PG9.0–19 Beta 3; its last measured boot default is replica in PG19 Beta 3, with postmaster context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
wal_log_hints
wal_log_hints — Writes full pages to WAL when first modified after a checkpoint, even for a non-critical modification. Observed in PG9.4–19 Beta 3; its last measured boot default is off in PG19 Beta 3, with postmaster context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
wal_recycle
wal_recycle recycles WAL files by renaming them. It is a superuser setting present in PG12–18; the latest recorded boot default is on.
wal_skip_threshold
wal_skip_threshold sets the minimum size of new file to fsync instead of writing WAL. It is a user setting present in PG13–18; the latest recorded boot default is 2 MiB.
wal_summary_keep_time
wal_summary_keep_time sets the time for which WAL summary files should be kept. It is a sighup setting present in PG17–18; the latest recorded boot default is 10 d.
wal_sync_method
wal_sync_method — Selects the method used for forcing WAL updates to disk. Observed in PG9.0–19 Beta 3; its last measured boot default is fdatasync in PG19 Beta 3, with sighup context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
wal_writer_delay
wal_writer_delay — Time between WAL flushes performed in the WAL writer. Observed in PG9.0–19 Beta 3; its last measured boot default is 200 ms in PG19 Beta 3, with sighup context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
wal_writer_flush_after
wal_writer_flush_after — Amount of WAL written out by WAL writer that triggers a flush. Observed in PG9.6–19 Beta 3; its last measured boot default is 1 MiB (128 × 8kB) in PG19 Beta 3, with sighup context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.