content_image/706841.jpg
| s2 | 3306 | ONLINE | | s1 | 3306 | ONLINE | +-------------+-------------+--------------+ 

<img src='content_image/706841.jpg'>

The member has now been restored to the group as a new member. 

## Note 

If the server you are restoring is a primary member, once it has gained synchrony with the group and become ONLINE , perform the steps described at the end of Restoring a Primary Member to revert the configuration changes you had made to the server before you started it. 

Restoring Persisted System Variables. mysqlbackup  does not provide support for backing up or preserving Section 5.1.9.3, “Persisted System Variables” —the file mysqld-auto.cnf  is not included in a backup. To start the restored member with its persisted variable settings, you need to do one of the following: 

•Preserve a copy of the mysqld-auto.cnf  file from the corrupted server, and copy it to the restored server’s data directory. 

•Copy the mysqld-auto.cnf  file from another member of the group into the restored server’s data directory, if that member has the same persisted system variable settings as the corrupted member. 

•After the restored server is started and before you restart Group Replication, set all the system variables manually to their persisted values through a mysql  client. 

Restoring a Primary Member.  If the restored member is a primary in the group, care must be taken to prevent writes to the restored database during the Group Replication distributed recovery process. Depending on how the group is accessed by clients, there is a possibility of DML statements being executed on the restored member once it becomes accessible on the network, prior to the member finishing its catch-up on the activities it has missed while off the group. To avoid this, before starting the restored server , configure the following system variables in the server option file: 

group_replication_start_on_boot=OFF super_read_only=ON event_scheduler=OFF 

These settings ensure that the member becomes read-only at startup and that the event scheduler is turned off while the member is catching up with the group during the distributed recovery process. Adequate error handling must also be configured on the clients, as they are prevented temporarily from performing DML operations during this period on the restored member. Once the restore process is fully completed and the restored member is in-sync with the rest of the group, revert those changes; restart the event scheduler: 

mysql> SET global event_scheduler=ON; 

Edit the following system variables in the member’s option file, so things are correctly configured for the next startup: 

## 18.6 Group Replication Security 

group_replication_start_on_boot=ON super_read_only=OFF event_scheduler=ON 

This section explains how to secure a group, securing the connections between members of a group, or by establishing a security perimeter using an IP address allowlist. 

