# pt-online-schema-change locking replication - troubleshoot

**URL:** <https://forums.percona.com/t/pt-online-schema-change-locking-replication-troubleshoot/7092>\
**Category:** Percona Toolkit\
**Created:** [July 2, 2019, 11:32am UTC](https://forums.percona.com/t/pt-online-schema-change-locking-replication-troubleshoot/7092 "2019-07-02T11:32:18Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![star2star\_lewis](https://avatars.discourse-cdn.com/v4/letter/s/c0e974/32.png) [@star2star\_lewis](https://forums.percona.com/u/star2star_lewis)\
**Post date:** [July 2, 2019, 11:32am UTC](https://forums.percona.com/t/pt-online-schema-change-locking-replication-troubleshoot/7092/1 "2019-07-02T11:32:18Z")

</div>

Running pr-online-schema-change on a slave to optimize a table. It is locking the table so replication is falling behind.  
I have run this successfully on this server and others, but the lock is happening on the latest run.  
What can I do to troubleshoot?

Server: Debian GNU/Linux 8.7 (jessie)  
Mysql version: 5.5.54-38.7-log  
pt-online-schema-change 3.0.12

command:  
/usr/bin/pt-online-schema-change --execute --print --alter " ENGINE=MyISAM " u=$user,p=$passwd,D=$DB,t=$TBL --no-check-replication-filters --recursion-method=none --critical-load Threads\_running=100

No slaves found. See --recursion-method if host [db4-dfw.star2star.com](http://db4-dfw.star2star.com) has slaves.  
Not checking slave lag because no slaves were found and --check-slave-lag was not specified.

2019-07-02T16:42:38 Copying approximately 3404389414 rows…  
INSERT LOW\_PRIORITY IGNORE INTO `starbox_cdr`.`_cdr_new` (`id`, `locationid`, `extensionid`, `accountcode`, `src`, `dst`, `dcontext`, `clid`, `channel`, `dstchannel`, `lastapp`, `lastdata`, `start`, `answer`, `end`, `duration`, `billsec`, `disposition`, `amaflags`, `src_display`, `dst_display`, `s2saccountcode`, `accid`, `cac`, `cac_display`, `pac`, `pac_display`) SELECT `id`, `locationid`, `extensionid`, `accountcode`, `src`, `dst`, `dcontext`, `clid`, `channel`, `dstchannel`, `lastapp`, `lastdata`, `start`, `answer`, `end`, `duration`, `billsec`, `disposition`, `amaflags`, `src_display`, `dst_display`, `s2saccountcode`, `accid`, `cac`, `cac_display`, `pac`, `pac_display` FROM `starbox_cdr`.`cdr` FORCE INDEX(`PRIMARY`) WHERE ((`id` \>= ?)) AND ((`id` \<= ?)) LOCK IN SHARE MODE /_pt-online-schema-change 23533 copy nibble_/  
SELECT /\*!40001 SQL\_NO\_CACHE \*/ `id` FROM `starbox_cdr`.`cdr` FORCE INDEX(`PRIMARY`) WHERE ((`id` \>= ?)) ORDER BY `id` LIMIT ?, 2 /_next chunk boundary_/

Id User Host/IP DB Time Cmd State Query

* * *

96625366 debian-sy localhost 0 Query show full processlist  
96625523 archiver localhost starbox\_cd 0 Query Sending INSERT LOW\_PRIORITY IG → pt-online-schema-change  
96469822 system us star2star 33 Connec Waiting INSERT IGNORE INTO sta → replication  
96625524 archiver localhost starbox\_cd 35 Sleep  
75161925 system us 13366097 Connec Waiting