MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6

17.5.1 Deploying in Multi-Primary or Single-Primary Mode

Group Replication operates in the following different modes:

The default mode is single-primary. It is not possible to have members of the group deployed in different modes, for example one configured in multi-primary mode while another one is in single-primary mode. To switch between modes, the group and not the server, needs to be restarted with a different operating configuration. Regardless of the deployed mode, Group Replication does not handle client-side fail-over, that must be handled by the application itself, a connector or a middleware framework such as a proxy or MySQL Router 8.0.

When deployed in multi-primary mode, statements are checked to ensure they are compatible with the mode. The following checks are made when Group Replication is deployed in multi-primary mode:

These checks can be deactivated by setting the option group_replication_enforce_update_everywhere_checks to FALSE. When deploying in single-primary mode, this option must be set to FALSE.