#### 18.8.3.1 Online Upgrade Considerations

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 When upgrading an online group you should consider the following points:

* Regardless of the way which you upgrade your group, it is important to disable any writes to group members until they are ready to rejoin the group.

* When a member is stopped, the [`super_read_only`](server-system-variables.html#sysvar_super_read_only) variable is set to on automatically, but this change is not persisted.

* When MySQL 5.7.22 or MySQL 8.0.11 tries to join a group running MySQL 5.7.21 or lower it fails to join the group because MySQL 5.7.21 does not send its value of [`lower_case_table_names`](server-system-variables.html#sysvar_lower_case_table_names).

