-<!-- $Header: /cvsroot/pgsql/doc/src/sgml/wal.sgml,v 1.5 2001/03/16 05:44:33 tgl Exp $ -->
+<!-- $Header: /cvsroot/pgsql/doc/src/sgml/wal.sgml,v 1.6 2001/05/15 13:57:37 momjian Exp $ -->
<chapter id="wal">
<title>Write-Ahead Logging (<acronym>WAL</acronym>)</title>
log (known as the redo record) it should start the REDO operation,
since any changes made to data files before that record are already
on disk. After a checkpoint has been made, any log segments written
- before the redo record are removed, so checkpoints are used to free
+ before the undo records are removed, so checkpoints are used to free
disk space in the <acronym>WAL</acronym> directory. (When
<acronym>WAL</acronym>-based <acronym>BAR</acronym> is implemented,
the log segments can be archived instead of just being removed.)