# Percona XtraDB and wsrep\_convert\_lock\_to\_trx

**URL:** <https://forums.percona.com/t/percona-xtradb-and-wsrep-convert-lock-to-trx/17782>\
**Category:** Percona XtraDB Cluster 8.x\
**Created:** [September 30, 2022, 8:51am UTC](https://forums.percona.com/t/percona-xtradb-and-wsrep-convert-lock-to-trx/17782 "2022-09-30T08:51:25Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![rj-db](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/rj-db/32/7945_2.png) [@rj-db](https://forums.percona.com/u/rj-db)\
**Post date:** [September 30, 2022, 8:51am UTC](https://forums.percona.com/t/percona-xtradb-and-wsrep-convert-lock-to-trx/17782/1 "2022-09-30T08:51:25Z")

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Hi,  
I have a question relating to a 3 node Percona XtraDB cluster for a Magento online store. The percona cluster is running on 3 Ubuntu nodes (5.4.0-126-generic #142-Ubuntu) and the version of percona is the latest from the repos. (percona-xtradb-cluster 1:8.0.29-21-1.focal).  
In order to get Magento to work I have always had to have the cluster set to a PERMISSIVE state (SET GLOBAL pxc\_strict\_mode=PERMISSIVE;) mainly because Magento issues GET\_LOCK and RELEASE\_LOCK on certain tables.

Now I have noticed that there is a wsrep variable in the percona documentation (that comes from galera I guess) as follows:

> **[Percona XtraDB Cluster - Index of wsrep system variables](https://docs.percona.com/percona-xtradb-cluster/8.0/wsrep-system-index.html)**
>
> Percona XtraDB Cluster introduces a number of MySQL system variables
> related to write-set replication.

### `wsrep_convert_lock_to_trx`

which looked like something promising to try. However, it does not appear to be an available variable on my percona instance - I have tried setting the variable directly:

SET GLOBAL wsrep\_convert\_LOCK\_to\_trx=1;

But I get:  
Error Code: 1193. Unknown system variable ‘wsrep\_convert\_LOCK\_to\_trx’

I’ve also tried setting it up in the configuration file, but again the variable is not recognised:  
#try turning on LOCKS to TRANSACTION conversion  
wsrep\_convert\_lock\_to\_trx=ON

Should this variable be available as specified in the documentation for Percona 8 or has it been deprecated / removed?

Many thanks for any help on this topic.

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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:** [October 3, 2022, 3:29pm UTC](https://forums.percona.com/t/percona-xtradb-and-wsrep-convert-lock-to-trx/17782/2 "2022-10-03T15:29:40Z")

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`GET_LOCK("foo", 10)` is not the same as `LOCK TABLE foo`. The former creates a lock on a randomly named object, much like a typical semaphore. The later will lock a specific table, named ‘foo’. These are two entirely different concepts. `wsrep_convert_lock_to_trx` was used to convert the later into transactions, not the former.

`wsrep_convert_lock_to_trx` was indeed removed but not from the docs. It is a documentation bug.  
[https://jira.percona.com/browse/PXC-2242](https://jira.percona.com/browse/PXC-2242)

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<div class="post-metadata">

**Author:** ![rj-db](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/rj-db/32/7945_2.png) [@rj-db](https://forums.percona.com/u/rj-db)\
**Post date:** [October 3, 2022, 4:01pm UTC](https://forums.percona.com/t/percona-xtradb-and-wsrep-convert-lock-to-trx/17782/3 "2022-10-03T16:01:35Z")

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Thx [Profile - matthewb - Percona Community Forum](https://forums.percona.com/u/matthewb) for the reply - greatly appreciated!

Ok - this all makes sense and thx for the clarity of your answer - it’s good to know I hadn’t missed something and it is just a documentation bug.

Many thx!