Unblocking a Partition Group replication enables you to reset the group membership list by forcing a specific configuration. For instance in the case above, where s1 and s2 are the only servers online, you could choose to force a membership configuration consisting of only s1 and s2. This requires checking some information about s1 and s2 and then using the  group_replication_force_members  variable. The table shows that s1 is now in a group that has no means of progressing without external intervention, because a majority of the servers are unreachable. In this particular case, the group membership list needs to be reset to allow the system to proceed, which is explained in this section. Alternatively, you could also choose to stop Group Replication on s1 and s2 (or stop completely s1 and s2), figure out what happened with s3, s4 and s5 and then restart Group Replication (or the servers). mysql>  SELECT MEMBER_ID,MEMBER_STATE FROM performance_schema.replication_group_members; +--------------------------------------+--------------+ | MEMBER_ID | MEMBER_STATE | +--------------------------------------+--------------+ | 1999b9fb-4aaf-11e6-bb54-28b2bd168d07 | UNREACHABLE | | 199b2df7-4aaf-11e6-bb16-28b2bd168d07 | ONLINE | | 199bb88e-4aaf-11e6-babe-28b2bd168d07 | ONLINE | | 19ab72fc-4aaf-11e6-bb51-28b2bd168d07 | UNREACHABLE | | 19b33846-4aaf-11e6-ba81-28b2bd168d07 | UNREACHABLE | +--------------------------------------+--------------+ mysql>  SELECT MEMBER_ID,MEMBER_STATE, MEMBER_ROLE FROM performance_schema.replication_group_members; +--------------------------------------+--------------+-------------+ | MEMBER_ID | MEMBER_STATE |-MEMBER_ROLE | +--------------------------------------+--------------+-------------+ | 1999b9fb-4aaf-11e6-bb54-28b2bd168d07 | ONLINE | SECONDARY | | 199b2df7-4aaf-11e6-bb16-28b2bd168d07 | ONLINE | PRIMARY | | 199bb88e-4aaf-11e6-babe-28b2bd168d07 | ONLINE | SECONDARY | | 19ab72fc-4aaf-11e6-bb51-28b2bd168d07 | ONLINE | SECONDARY | | 19b33846-4aaf-11e6-ba81-28b2bd168d07 | ONLINE | SECONDARY | +--------------------------------------+--------------+-------------+ Initially the group is running fine and the servers are happily communicating with each other. You can verify this by logging into s1 and looking at its  replication_group_members  performance schema table. For example: However, moments later there is a catastrophic failure and servers s3, s4 and s5 stop unexpectedly. A few seconds after this, looking again at the  replication_group_members  table on s1 shows that it is still online, but several others members are not. In fact, as seen below they are marked as  UNREACHABLE . Moreover, the system could not reconfigure itself to change the membership, because the majority has been lost. 3754 Network Partitioning •Server s5 with member identifier  19b33846-4aaf-11e6-ba81-28b2bd168d07