Note
For V4.2.5, this parameter is available starting with V4.2.5 BP5.
Description
zone_deploy_mode specifies the deployment mode of a tenant across zones.
Privilege requirements
Query the parameter
systenant and all user tenants can query this parameter by using theSHOW PARAMETERSstatement or theGV$OB_PARAMETERSview.Modify the parameter
systenant and user tenants can modify 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
By default, new tenants and upgraded existing tenants are deployed in homogeneous zone mode. In homogeneous zone mode, the number of units in each zone must be the same, and log streams are symmetrically distributed across zones. Log streams are bound to unit groups:
Each unit group consists of one unit from each zone, and each unit belongs to only one unit group.
Each log stream belongs to only one unit group, and its replicas 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_NUMvalue of each zone must be adjusted to remain consistent.
To enable heterogeneous zone mode, set the zone_deploy_mode parameter to hetero. Once set, you cannot change the value back to homo.
Compared with homogeneous zone mode, heterogeneous zone mode has the following differences:
Log streams are no longer bound to unit groups, and their replicas are not restricted to symmetric units in each zone.
The
UNIT_NUMvalues of different resource pools in a tenant can be different, but there can be at most two differentUNIT_NUMvalues.You can modify the
UNIT_NUMvalue of a specific resource pool to scale in or out the number of units at the resource pool level.When you use the
ALTER RESOURCE TENANTstatement to reduce theUNIT_NUMvalue to scale in, you cannot specify theUNIT_GROUPparameter.When you use the
ALTER SYSTEM CREATE LSorALTER SYSTEM MODIFY LSstatement to manage log streams, you cannot specify theUNIT_GROUPparameter.
Examples
Set the deployment mode of a tenant to heterogeneous zone mode.
obclient> ALTER SYSTEM SET zone_deploy_mode = 'hetero';