pg_xlogdump man page

pg_xlogdump — display a human-readable rendering of the write-ahead log of a PostgreSQL database cluster


pg_xlogdump [option...] [startseg [endseg]]


pg_xlogdump displays the write-ahead log (WAL) and is mainly useful for debugging or educational purposes.

This utility can only be run by the user who installed the server, because it requires read-only access to the data directory.


The following command-line options control the location and format of the output:


Start reading at the specified log segment file. This implicitly determines the path in which files will be searched for, and the timeline to use.


Stop after reading the specified log segment file.

Output detailed information about backup blocks.
-e end
Stop reading at the specified log position, instead of reading to the end of the log stream.
After reaching the end of valid WAL, keep polling once per second for new WAL to appear.
-n limit
Display the specified number of records, then stop.
-p path
Directory in which to find log segment files. The default is to search for them in the pg_xlog subdirectory of the current directory.
-r rmgr
Only display records generated by the specified resource manager. If list is passed as name, print a list of valid resource manager names, and exit.
-s start
Log position at which to start reading. The default is to start reading the first valid log record found in the earliest file found.
-t timeline
Timeline from which to read log records. The default is to use the value in startseg, if that is specified; otherwise, the default is 1.
Print the pg_xlogdump version and exit.
-x xid
Only display records marked with the given transaction ID.
Display summary statistics (number and size of records and full-page images) instead of individual records. Optionally generate statistics per-record instead of per-rmgr.
Show help about pg_xlogdump command line arguments, and exit.


Can give wrong results when the server is running.

Only the specified timeline is displayed (or the default, if none is specified). Records in other timelines are ignored.

pg_xlogdump cannot read WAL files with suffix .partial. If those files need to be read, .partial suffix needs to be removed from the file name.

See Also

Section 30.5, “WAL Internals”, in the documentation


PostgreSQL 9.6.0 2016