# Cluster hangs during alter table command

**URL:** <https://forums.percona.com/t/cluster-hangs-during-alter-table-command/6413>\
**Category:** Percona XtraDB Cluster 5.x\
**Created:** [June 14, 2018, 7:07am UTC](https://forums.percona.com/t/cluster-hangs-during-alter-table-command/6413 "2018-06-14T07:07:47Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![jhbremer](https://avatars.discourse-cdn.com/v4/letter/j/bbce88/32.png) [@jhbremer](https://forums.percona.com/u/jhbremer)\
**Post date:** [June 14, 2018, 7:07am UTC](https://forums.percona.com/t/cluster-hangs-during-alter-table-command/6413/1 "2018-06-14T07:07:47Z")

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We have a three node cluster on PXC 5.5. Writes happen on only one of the nodes. Whenever we alter a table (specifically very large tables), the entire cluster hangs. Process list shows many connections in state ‘wsrep in pre-commit stage’ on the main write node. These are queries pointing to tables not related to the alter table.

Is this simply a case of one of the nodes causing flow control? We have plans to replace our slowest node very soon, so I’m hoping it’s that. If we were less concerned about a single node being slightly behind, would increasing fc\_limit help the cluster from getting hung up during alters?