# what's meaning of last\_lsn?

**URL:** <https://forums.percona.com/t/whats-meaning-of-last-lsn/2313>\
**Category:** Percona XtraBackup\
**Created:** [November 29, 2012, 3:13am UTC](https://forums.percona.com/t/whats-meaning-of-last-lsn/2313 "2012-11-29T03:13:34Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![liyx](https://avatars.discourse-cdn.com/v4/letter/l/59ef9b/32.png) [@liyx](https://forums.percona.com/u/liyx)\
**Post date:** [November 29, 2012, 3:13am UTC](https://forums.percona.com/t/whats-meaning-of-last-lsn/2313/1 "2012-11-29T03:13:34Z")

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When i use innobackup to backup my database.It will write database’s checkpoint to file named xtrabackup\_checkpoint.In the file ,i don’t know the meaning of last\_lsn .  
What is difference of last\_lsn and to\_lsn? Where can i use it?  
Please help me!

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**Author:** ![revin](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/revin/32/824_2.png) [@revin](https://forums.percona.com/u/revin)\
**Post date:** [December 4, 2012, 5:29pm UTC](https://forums.percona.com/t/whats-meaning-of-last-lsn/2313/2 "2012-12-04T17:29:58Z")

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liyx,

This pages has related information:

[http://www.mysqlperformanceblog.com/2012/02/17/the-relations](http://www.mysqlperformanceblog.com/2012/02/17/the-relations) hip-between-innodb-log-checkpointing-and-dirty-buffer-pool-p ages/  
[http://www.percona.com/files/percona-live/justin-innodb-inte](http://www.percona.com/files/percona-live/justin-innodb-inte) rnals.pdf

In short, LSN (log sequence number) are offsets from the redo logs - so simply put, last\_lsn is the offset where the last transaction written to the redo logs was written. to\_lsn on the other hand, should be paired to a from\_lsn, mostly useful on incremental backups, etc.