enable_transfer

Description

enable_transfer specifies whether to allow Transfer operations within a tenant.

Privilege requirements

• Query the parameter

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

• Modify the parameter

  The sys tenant and user tenants can modify this parameter.

Attributes

Considerations

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

The enable_rebalance parameter is used to control whether to perform load balancing between tenants in the sys tenant and whether to perform load balancing within a tenant in a user tenant. The default value is true. The setting takes effect immediately without requiring a restart of 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 requiring a restart of the OBServer node. The meaning of the value of the enable_transfer parameter depends on the value of the enable_rebalance parameter:

• When the value of the enable_rebalance parameter is false, the system does not automatically perform load balancing, regardless of whether the value of the enable_transfer parameter is true or false. To disable all load balancing, run the following commands:

  obclient> ALTER SYSTEM SET enable_rebalance=false;
  

• When the values of both the enable_rebalance and enable_transfer parameters are true, the system automatically adjusts the distribution of partitions during tenant scaling operations to achieve load balancing. It dynamically adjusts the number of log streams based on the load balancing algorithm and automatically performs leader and partition balancing within the tenant. To achieve this, run the following commands:

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

• When the value of the enable_rebalance parameter is true and the value of the enable_transfer parameter is false, the system cannot initiate Transfer operations during tenant scaling. It can only achieve limited load balancing through log stream migration. It performs log stream balancing based on the existing log streams without initiating Transfer operations or dynamically changing the number of log streams. To achieve this, run the following commands:

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

Examples

• Set the load balancing strategy for a specified tenant in the sys tenant.

  • Enable tenant-level load balancing and the Transfer feature within the tenant for a specified tenant.

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

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

    The preceding statements specify that the values of the enable_rebalance and enable_transfer parameters for the specified tenant are true.

  • Enable tenant-level load balancing and the Transfer feature within the tenant for all user tenants (excluding the sys tenant and the Meta 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;
    

    The preceding statements specify that the values of the enable_rebalance and enable_transfer parameters for all user tenants are true.

    Note

    Starting from V4.2.1, OceanBase Database treats TENANT = all_user and TENANT = all as equivalent. To apply the setting to all user tenants, we recommend that you use TENANT = all_user. The TENANT = all option will be deprecated in later versions.

• Set the load balancing strategy for the current tenant in a user tenant.

  MySQL mode

  Oracle mode

  To enable tenant-level load balancing and the Transfer feature within the tenant in a MySQL tenant, run the following commands:

  obclient> ALTER SYSTEM SET enable_rebalance = true;
  

  obclient> ALTER SYSTEM SET enable_transfer = true;
  

  To enable tenant-level load balancing and the Transfer feature within the tenant in an Oracle tenant, run the following commands:

  obclient> ALTER SYSTEM SET enable_rebalance = 'true';
  

  obclient> ALTER SYSTEM SET enable_transfer = 'true';
  

References

• Scale in and out a tenant by adjusting the number of units
• Scale in and out a tenant by adjusting the primary zone
• enable_rebalance