Note
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 the value of this parameter.
Attributes
| Attribute | Description |
|---|---|
| Parameter 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. The setting takes effect immediately. |
Considerations
For a new tenant or an upgraded existing tenant, the default value of this parameter is homo. In homogeneous zone mode, the number of units in each zone must be the same. Log streams are evenly 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 the log stream are distributed across the units in the unit group.
When you scale in or out the number of units, you must do so at the unit group level. The
UNIT_NUMof each zone must be adjusted to ensure consistency.
To enable heterogeneous zone mode, set the value of this parameter to hetero. Once you change the value to hetero, you cannot change it back to homo.
Compared with homogeneous zone mode, heterogeneous zone mode has the following differences:
Log streams are no longer bound to unit groups. The replicas of log streams are no longer limited to symmetric units in each zone.
The
UNIT_NUMvalues of resource pools in a tenant can be different. However, at most two differentUNIT_NUMvalues are allowed.You can modify the
UNIT_NUMvalue of a specific resource pool to scale in or out 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 manage a log stream, you cannot specify theUNIT_GROUPparameter.
Examples
Set the distribution mode of a tenant to heterogeneous zone mode.
obclient> ALTER SYSTEM SET zone_deploy_mode = 'hetero';
References
- For more information about how to create a tenant in heterogeneous zone mode, see Create a tenant.