# Pt-table-checksum causing lag on replica - suggestions

**URL:** <https://forums.percona.com/t/pt-table-checksum-causing-lag-on-replica-suggestions/10604>\
**Category:** Percona Toolkit\
**Tags:** percona\
**Created:** [May 26, 2021, 6:58pm UTC](https://forums.percona.com/t/pt-table-checksum-causing-lag-on-replica-suggestions/10604 "2021-05-26T18:58:14Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Ron](https://avatars.discourse-cdn.com/v4/letter/r/ecae2f/32.png) [@Ron](https://forums.percona.com/u/Ron)\
**Post date:** [May 26, 2021, 6:58pm UTC](https://forums.percona.com/t/pt-table-checksum-causing-lag-on-replica-suggestions/10604/1 "2021-05-26T18:58:14Z")

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Hello, I’m running pt-table-checksum on a master database and it’s creating too much lag on its replica. Checksum queries are causing the replica to lag further and further behind. Before running pt-table-checksum the replica was able to keep up with its master. What is the best method to keep the replica from falling behind? I see pt-table-checksum has a number of options related to lag such as --check-slave-lag and --max-load. Some of the innodb tables that are being checked are over a million records large.  
Thanks.

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**Author:** ![matthewb](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/matthewb/32/34_2.png) [@matthewb](https://forums.percona.com/u/matthewb)\
**Post date:** [May 26, 2021, 7:13pm UTC](https://forums.percona.com/t/pt-table-checksum-causing-lag-on-replica-suggestions/10604/2 "2021-05-26T19:13:19Z")

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Hi @Ron,  
Yes, certainly take advantage of --check-slave-lag which will pause the checksum process if your replica’s start lagging behind and auto-resumes when they catch up. Also, you might try lowering --chunk-time so that less rows are calculated each chunk, thereby processing faster and causing less lag.