server_permanent_offline_time

Description

server_permanent_offline_time specifies the time threshold for a node to be considered permanently offline after its heartbeat is lost. When a node is permanently offline, the Root Service processes the data replicas on the OBServer node, removes the data replicas from the Paxos member group, and replicates the data replicas to other available OBServer nodes to ensure the integrity of the Paxos member group.

Privilege requirements

• Query the parameter

  The sys tenant and all user tenants can query the parameter by using the SHOW PARAMETERS statement or the GV$OB_PARAMETERS view.

• Modify the parameter

  Only the sys tenant can modify the parameter. User tenants cannot modify the parameter.

Attributes

Considerations

By setting this parameter, you can avoid unnecessary replica replication. The system only starts the replication of data replicas on permanently offline nodes when the replicas are lost for a duration exceeding the specified threshold.

The applicable scenarios and recommended values of this parameter are as follows:

• OceanBase Database version upgrade: We recommend that you set the value of this parameter to 72h.

  Note

  When you use OCP V2.3.5 or later to upgrade OceanBase Database V2.1.2 or later, the system automatically sets the value of this parameter to 72h.

• Hardware replacement of OBServer nodes: We recommend that you set the value of this parameter to 4h.

• Clearing and online activation of OBServer nodes: We recommend that you set the value of this parameter to 10m to enable the cluster to go online quickly.

Examples

Set the time threshold for a node to be considered permanently offline after its heartbeat is lost to 3600s.

obclient> ALTER SYSTEM SET server_permanent_offline_time = '3600s';

References

For more information about the Root Service, see Database-layer high availability.