enable_rebalance

Description

enable_rebalance specifies whether to enable the automatic load balancing feature.

The value of this parameter in different tenants controls the different balancing operations.

• In the system tenant, this parameter specifies whether to enable cross-tenant load balancing.

  • false: The system does not perform background unit migration. However, when a node is offline or in the DELETING state, this parameter does not affect unit migration.
  • true: The system can perform unit migration to balance the load.

• In a user tenant, this parameter specifies whether to enable intra-tenant load balancing.

  • false: Load balancing will not be performed for this tenant. Any ongoing balancing operations will be canceled. If you perform a scaling operation under this condition, an error will be returned. For example, an error will be returned when you perform the following operations:

    • Increase or decrease the number of resource units for the tenant.

    • Change the primary zone of the first priority, provided that the primary zone of the first priority does not change, no error will be returned.

    • If the primary zone is RANDOM, change the number of F replicas.

    Note

    For V4.2.5:

    • Starting from V4.2.5 BP5, when the enable_rebalance parameter is set to false, the system will not return an error when you increase or decrease the number of resource units for the tenant.
    • Starting from V4.2.5 BP1, when the enable_rebalance parameter is set to false, the system will not return an error when you change the primary zone of the first priority or change the number of F replicas, provided that the primary zone is RANDOM.
    • Although the above operations will not return an error after the enable_rebalance parameter is set to false, log load balancing is still not initiated. You can perform the required changes by using this parameter in batch, and then enable load balancing after all changes are completed.

  • true: Load balancing will be performed for the tenant.

Privilege requirements

• Query the parameter

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

• Modify the parameter

  You can set the enable_rebalance parameter for the sys tenant and user tenants.

Attributes

Examples

• Disable both cross-tenant and intra-tenant load balancing.

  obclient> ALTER SYSTEM SET enable_rebalance = false tenant = all_user;
  

• Enable only cross-tenant load balancing.

  obclient> ALTER SYSTEM SET enable_rebalance = true tenant='all_user';
  

• Disable cross-tenant load balancing and enable intra-tenant load balancing.

  obclient> ALTER SYSTEM SET enable_rebalance = false tenant='all_user';
            ALTER SYSTEM SET enable_rebalance = true tenant='MYSQL';
  

References

• Scale in and out the number of resource units for a tenant
• Scale in and out the number of resource units for a tenant by changing the primary zone
• Balance resource units