zone_disk_balance_tolerance_percentage

Overview

The zone_disk_balance_tolerance_percentage parameter specifies the tolerance for disk imbalance in the inter-zone table group disk balancing algorithm. Disk balancing between zones is triggered only when the difference between the disk usage of the zone with the highest disk usage and the zone with the lowest disk usage exceeds the maximum disk usage of that zone multiplied by this percentage.

Privilege requirements

• Query parameters

  The SHOW PARAMETERS statement or the GV$OB_PARAMETERS view can be used by the sys tenant and all user tenants to query this parameter.

• Modify parameters

  Both the sys tenant and user tenants can modify this parameter.

Attributes

Usage instructions

The load balancing module automatically attempts to exchange SCOPE=ZONE table groups located on different zones to achieve a balanced total disk usage for these tables across all zones. To control the frequency of such exchanges, an exchange is only attempted when the difference in total disk usage of SCOPE=ZONE table groups between zones meets either of the following two conditions:

1. The total disk usage of the table group differs by more than the maximum zone's total disk usage multiplied by zone_disk_balance_tolerance_percentage/100.

2. The total disk capacity of the largest zone exceeds 50 GB * number of log stream groups.

In general, you can keep the default value of the zone_disk_balance_tolerance_percentage parameter, which is 10.

• When the disk usage of tables with SCOPE = 'ZONE' fluctuates significantly, causing a high frequency of inter-zone disk balancing and wishing to reduce this frequency, you can appropriately increase this value.

• To completely disable inter-zone disk balancing, set this value to 100.

Configuration example

Set the tolerance percentage for inter-zone disk balancing to 20%.

obclient> ALTER SYSTEM SET zone_disk_balance_tolerance_percentage = 20;