Note
For V1.4, this parameter is available starting with V1.4.
Description
freeze_trigger_percentage specifies the threshold percentage of the tenant's MemStore memory usage that triggers a freeze.
Privilege requirements
Query the parameter
The
systenant and all user tenants can use theSHOW PARAMETERSstatement or theGV$OB_PARAMETERSview to query this parameter.Modify the parameter
The
systenant and user tenants can modify this parameter.
Attributes
| Attribute | Description |
|---|---|
| Type | Int |
| Default value | 20
NoteFor V4.0.0, the default value is changed from 70 to 20. |
| Value range | (0, 100) |
| 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
OceanBase Database stores the most recent data in MemStore. To prevent memory overflow, the system provides two important protection mechanisms:
Freeze mechanism: Persists data in memory to disk to release memory space.
Throttling mechanism: Reduces the write speed when memory pressure is high to gain time for memory release.
These two mechanisms are controlled by two tenant-level parameters:
freeze_trigger_percentage(freeze threshold) and writing_throttling_trigger_percentage (throttling threshold).To avoid performance degradation caused by premature throttling, the value of writing_throttling_trigger_percentage must be greater than the value of
freeze_trigger_percentage.You can adjust the proportion of MemStore memory in a tenant by using the following parameters:
When the active MemStore memory usage of a tenant reaches
freeze_trigger_percentage * memstore_limit(wherememstore_limit = tenant memory * memstore_limit_percentage), the system automatically triggers a freeze (a prerequisite for a dump) and then schedules a dump. After the dump, the system releases the occupied MemStore memory.When memory is insufficient, you can increase the value of
memstore_limit_percentageand decrease the value offreeze_trigger_percentageto temporarily expand memory and accelerate the dump process. Thememstore_limit_percentageparameter controls the proportion of tenant memory available for MemStore writes. The default value is 0, indicating that the system adaptively adjusts the proportion of tenant memory available for MemStore writes.
Examples
Set the threshold percentage of the tenant's MemStore memory usage that triggers a freeze to 20%.
obclient> ALTER SYSTEM SET freeze_trigger_percentage=20;