Note
- For V4.6.x, this parameter is available starting with V4.6.0.
- For V4.4.x, this parameter is available starting with V4.4.2.
- For V4.2.5, this parameter is available starting with V4.2.5 BP5.
Description
zone_deploy_mode specifies the distribution mode of a tenant across zones.
Privilege requirements
Query the parameter
The
systenant and all user tenants can query the value of this parameter by using theSHOW PARAMETERSstatement or theGV$OB_PARAMETERSview.Modify the parameter
The
systenant and user tenants can modify this parameter.
Attributes
Attribute |
Description |
|---|---|
| Type | String |
| Default value | homo |
| Value range |
|
| Modifiable | Yes. You can use the ALTER SYSTEM SET statement to modify the parameter. |
| Effective upon OBServer node restart | No |
Considerations
By default, new tenants and upgraded existing tenants are in the homogeneous zone mode. In the homogeneous zone mode, the number of units in each zone must be the same. The log streams are symmetrically distributed across zones and bound to unit groups:
A unit group consists of one unit from each zone. Each unit belongs to only one unit group.
A log stream belongs to only one unit group. The replicas of a log stream are distributed across the units in the unit group.
When you scale in or out units, you must do so at the unit group level. The
UNIT_NUMvalue of each zone must be adjusted to ensure consistency.
To enable the heterogeneous zone mode, set the value of the zone_deploy_mode parameter to hetero. After the parameter is set to hetero, you cannot change it back to homo.
The heterogeneous zone mode differs from the homogeneous zone mode in the following aspects:
The concept of unit groups no longer exists. The replicas of log streams are no longer limited to symmetric units in each zone.
The
UNIT_NUMvalues of the resource pools of a tenant can be different, but only two different values are allowed.You can modify the
UNIT_NUMvalue of a resource pool to scale in or out the resources of the resource pool.When you use the
ALTER RESOURCE TENANTstatement to scale in a tenant by reducing theUNIT_NUMvalue, you cannot specify theUNIT_GROUPparameter.When you use the
ALTER SYSTEM CREATE LSorALTER SYSTEM MODIFY LSstatement to modify a log stream, you cannot specify theUNIT_GROUPparameter.
Examples
Set the distribution mode of a tenant across zones to the heterogeneous zone mode.
obclient> ALTER SYSTEM SET zone_deploy_mode = 'hetero';