MODIFY LS

Purpose

This statement is used to change a log stream, including modifying the UNIT_GROUP (Homogeneous Zone mode) or UNIT_LIST (Heterogeneous Zone mode) of the log stream distribution, as well as the PRIMARY_ZONE of the log stream.

Limitations and considerations

• In OceanBase Database V4.2.5, this statement must be executed in V4.2.5 BP1 or later.

• In OceanBase Database of a version earlier than V4.x, only the Homogeneous Zone mode is supported for tenants. In OceanBase Database V4.2.5, the Heterogeneous Zone mode is supported for tenants starting from V4.2.5 BP5. Specifically:

  • In the Homogeneous Zone mode, the UNIT_GROUP of the log stream distribution and the PRIMARY_ZONE of the log stream can be modified.
  • In the Heterogeneous Zone mode, the UNIT_LIST of the log stream distribution and the PRIMARY_ZONE of the log stream can be modified.

• When changing a log stream, the log stream must exist and be in the NORMAL state.

• When changing a log stream, the tenant status of the log stream must be NORMAL.

  Note

  In OceanBase Database V4.2.5 BP1, the tenant status of the log stream cannot be CREATING or DROPPING.

• When modifying the UNIT_GROUP (Homogeneous Zone mode) or UNIT_LIST (Heterogeneous Zone mode) of the log stream distribution for a primary tenant, no load balancing task is running for all log streams of the tenant.

• We recommend that you do not modify the UNIT_GROUP (Homogeneous Zone mode) or UNIT_LIST (Heterogeneous Zone mode) attribute of the log stream distribution for a standby tenant. This is because the UNIT_GROUP or UNIT_LIST attribute of the log stream is automatically adjusted for a standby tenant, and manually modifying the attribute may not take effect.

• When modifying the UNIT_GROUP (Homogeneous Zone mode) or UNIT_LIST (Heterogeneous Zone mode) of the log stream distribution, the status of the target UNIT_GROUP or UNIT_LIST must be ACTIVE.

• When modifying the PRIMARY_ZONE of a log stream, make sure that the modified zone is included in the ZONE_LIST of the tenant. For a log stream, you can specify only one zone as the PRIMARY_ZONE, such as z1 or z2. You cannot specify z1,z2, z1; z2, or RANDOM for a log stream.

• When changing a log stream, the value of the tenant-level parameter enable_rebalance must be False. If enable_rebalance is set to True, the load balancing module of the tenant may automatically adjust the PRIMARY_ZONE and UNIT_GROUP or UNIT_LIST attribute of the log stream.

• In the Homogeneous Zone mode, only broadcasted log streams and system log streams (Log Stream 1) support setting the UNIT_GROUP to 0.

• In the Heterogeneous Zone mode, the UNIT_LIST specified for user log streams must not be empty.

Privilege requirements

To execute this statement, you must have the ALTER SYSTEM privilege. For more information about the privileges of OceanBase Database, see Privilege types in MySQL mode and Privilege types in Oracle mode.

Syntax

ALTER SYSTEM MODIFY LS
    LS [=] ls_id
    [UNIT_GROUP [=] unit_group_id] | [UNIT_LIST [=] (unit_id_list) ]
    [,PRIMARY_ZONE [=] 'zone_name'] 
    [TENANT [=] 'tenant_name'];

Parameters

Examples