enable_transfer

Description

enable_transfer specifies whether to allow transfer within a tenant. This parameter is invalid when enable_rebalance is set to False.

Attributes

Considerations

The load balancing strategy for a tenant is jointly controlled by the tenant-level parameters enable_rebalance and enable_transfer.

You can specify the enable_rebalance parameter in the sys tenant to control whether to enable load balancing among tenants, and specify this parameter in a user tenant to control whether to enable load balancing for the current tenant. The default value is true. The setting takes effect immediately without the need to restart the OBServer node.

You can specify the enable_transfer parameter to control whether to enable the transfer feature for a tenant. The default value is true. The setting takes effect immediately without the need to restart the OBServer node. The enable_transfer parameter depends on the value of the enable_rebalance parameter.

• If the value of enable_rebalance is false, the system does not perform automatic load balancing regardless of whether the value of enable_transfer is true or false. The command to disable load balancing is as follows:

  obclient> ALTER SYSTEM SET enable_rebalance=false;
  

• If the value of enable_rebalance is true and the value of enable_transfer is true, the system automatically adjusts partition distribution to achieve load balancing during a tenant scaling operation. You can dynamically adjust the number of log streams for a tenant based on the load balancing algorithm and enable automatic leader balancing and partition balancing in the tenant as follows:

  obclient> ALTER SYSTEM SET enable_rebalance=true;
  obclient> ALTER SYSTEM SET enable_transfer=true;
  

• If the value of enable_rebalance is true and the value of enable_transfer is false, the system cannot initiate transfer operations during tenant scaling, but can implement limited load balancing through log stream migration. You can balance existing log streams without transfer or dynamic changes in the number of log streams as follows:

  obclient> ALTER SYSTEM SET enable_rebalance=true;
  obclient> ALTER SYSTEM SET enable_transfer=false;
  

Examples

• Enable load balancing for a specified tenant from the sys tenant

  • Enable load balancing and the transfer feature for a specified tenant from the sys tenant

    obclient> ALTER SYSTEM SET enable_rebalance = true TENANT = 'tenant_name';
    

    obclient> ALTER SYSTEM SET enable_transfer = true TENANT = 'tenant_name';
    

    These statements only set the values of the enable_rebalance and enable_transfer parameters to true for the specified user tenant.

  • Enable intra-tenant load balancing and the transfer feature for all user tenants from the sys tenant

    obclient> ALTER SYSTEM SET enable_rebalance = true TENANT = all_user;
    

    obclient> ALTER SYSTEM SET enable_transfer = true TENANT = all_user;
    

    or

    obclient> ALTER SYSTEM SET enable_rebalance = true TENANT = all;
    

    obclient> ALTER SYSTEM SET enable_transfer = true TENANT = all;
    

    These statements only set the values of the enable_rebalance and enable_transfer parameters to true for all user tenants.

    Note

    In OceanBase Database V4.2.1 and later, TENANT = all_user and TENANT = all express the same semantics. If you want an operation to take effect on all user tenants, we recommend that you use TENANT = all_user. TENANT = all will be deprecated.

• Enable load balancing for a user tenant from the current tenant

  MySQL mode

  Oracle mode

  You can execute the following statements to enable load balancing and the transfer feature for a MySQL tenant:

  obclient> ALTER SYSTEM SET enable_rebalance = true;
  

  obclient> ALTER SYSTEM SET enable_transfer = true;
  

  You can execute the following statements to enable load balancing and the transfer feature for an Oracle tenant:

  obclient> ALTER SYSTEM SET enable_rebalance = 'true';
  

  obclient> ALTER SYSTEM SET enable_transfer = 'true';
  

References

• Modify the number of resource units for a tenant
• Modify the number of primary zones for a tenant
• enable_transfer