enable_transfer

Description

The enable_transfer parameter specifies whether to allow data transfer within a tenant. This parameter is ineffective when the enable_rebalance parameter is set to false.

Attributes

Usage notes

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

The enable_rebalance parameter specifies whether to enable load balancing among tenants. In a user tenant, this parameter specifies whether to enable load balancing within the tenant. The default value is true. The setting takes effect immediately without the need to restart the OBServer node.

The enable_transfer parameter specifies whether to enable the transfer feature within 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 enable_rebalance is set to 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 all load balancing features is as follows:

  obclient> ALTER SYSTEM SET enable_rebalance=false;
  

• If enable_rebalance is set to true and enable_transfer is set to true, the system automatically adjusts partition distribution during tenant scaling to achieve load balancing. The commands to dynamically adjust the number of log streams in a tenant and automatically perform leader and partition balancing are as follows:

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

• If enable_rebalance is set to true and enable_transfer is set to false, the system cannot initiate transfer operations during tenant scaling, but can implement limited load balancing through log stream migration. The command to perform log stream balancing based on the existing log streams without generating transfers or dynamic changes in the number of log streams is as follows:

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

Examples

• The system tenant configures the load balancing strategy for a specified tenant.

  • The system tenant enables intra-tenant load balancing and the transfer feature for a specified tenant.

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

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

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

  • The system tenant enables intra-tenant load balancing and the transfer feature for all user tenants (excluding the sys and meta tenants).

    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 set the enable_rebalance and enable_transfer parameters to true for all user tenants.

    Note

    Starting from OceanBase Database V4.2.1, 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.

• A user tenant configures the load balancing strategy for the current tenant.

  MySQL mode

  Oracle mode

  You can execute the following statements to enable intra-tenant 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 intra-tenant 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

• Scale a tenant up or down by adjusting the unit number
• Scale a tenant up or down by adjusting the primary zone
• enable_rebalance