PostgreSQL参数学习：wal_keep_segments

最新推荐文章于 2025-06-25 08:54:32 发布

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原文链接：https://yq.aliyun.com/articles/356630

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#数据库

本文详细介绍了PostgreSQL中wal_keep_segments参数的作用与设置方法。该参数用于指定在pg_xlog目录下保留的最小数量的日志文件段数，以便备用服务器进行流复制。如果设置不当可能导致日志丢失及复制连接中断。

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http://www.postgresql.org/docs/9.3/static/runtime-config-replication.html

参考官方文档：

wal_keep_segments (integer)
Specifies the minimum number of past log file segments kept in the pg_xlog directory, in case a standby server needs to fetch them for streaming replication. Each segment is normally 16 megabytes. If a standby server connected to the sending server falls behind by more than wal_keep_segments segments, the sending server might remove a WAL segment still needed by the standby, in which case the replication connection will be terminated. Downstream connections will also eventually fail as a result. (However, the standby server can recover by fetching the segment from archive, if WAL archiving is in use.)

This sets only the minimum number of segments retained in pg_xlog; the system might need to retain more segments for WAL archival or to recover from a checkpoint. If wal_keep_segments is zero (the default), the system doesn't keep any extra segments for standby purposes, so the number of old WAL segments available to standby servers is a function of the location of the previous checkpoint and status of WAL archiving. This parameter can only be set in the postgresql.conf file or on the server command line.

如果此值过小，那么在没有archive_log、而master很繁忙产生大量数据的前提下，wal log会丢失，复制用到的连接会被断掉的。

本文转自健哥的数据花园博客园博客，原文链接：http://www.cnblogs.com/gaojian/p/3355431.html，如需转载请自行联系原作者