Modify resource specification (unit config)

Modifying a resource specification means increasing or decreasing the CPU, memory, log disk capacity, and other settings in the resource specification.

Considerations

Before modifying a resource specification, if the unit corresponding to the resource specification is being used by a tenant and you confirm that resources need to be increased, you must ensure that each node has sufficient remaining resources for allocation during the increase process. You can query the oceanbase.GV$OB_SERVERS view for the total resources and allocated resources on each node, and then determine whether the resource specification can be modified through calculation.

To increase the resource specification, the total resources after modification must meet the following requirements:

Sum(min_cpu) <= CPU_CAPACITY;
Sum(max_cpu) <= CPU_CAPACITY * resource_hard_limit;
Sum(memory_size) <= MEM_CAPACITY;
Sum(log_disk_size) <= LOG_DISK_CAPACITY;

where:

• CPU_CAPACITY: the total CPU capacity on a single node.

• MEM_CAPACITY: the total memory capacity on a single node.

• LOG_DISK_CAPACITY: the total log disk capacity on a single node.

  The total log disk capacity is jointly controlled by the cluster-level parameters log_disk_size and log_disk_percentage. The log_disk_size parameter is used to set the size of the Redo log disk, and its default value is 0. The log_disk_percentage parameter is used to set the percentage of the total disk space occupied by Redo logs, and its default value is 0. The usage rules for the two parameters are as follows:

  • If the value of log_disk_size is 0M and the value of log_disk_percentage is not 0, the system allocates log disk space based on the value of log_disk_percentage.

  • If the value of log_disk_size is not 0M, the system allocates log disk space based on the value of log_disk_size regardless of whether the value of log_disk_percentage is 0.

  • If the value of log_disk_size is 0M and the value of log_disk_percentage is 0, the system automatically calculates the percentage of the total disk space occupied by Redo logs based on whether logs and data share the same disk:

    • When shared, the percentage of the total disk space occupied by Redo logs is 30%.

    • When exclusive, the percentage of the total disk space occupied by Redo logs is 90%.

  For more information about the log_disk_size parameter, see log_disk_size.

  For more information about the log_disk_percentage parameter, see log_disk_percentage.

• resource_hard_limit: the value of a parameter.

  When allocating units, the system allocates CPU resources based on the value of the resource_hard_limit parameter. The default value is 100, indicating that overprovisioning is not allowed. The value range is [100, 10000].

  For more information about the resource_hard_limit parameter, see resource_hard_limit.

To decrease the resource specification, ensure that the total CPU, memory, log disk capacity, and other resources after modification are greater than or equal to the currently used log disk space.

Limitations

Only the sys tenant can modify resource specifications.

Procedure

When modifying a resource specification, you can modify one or more of the CPU, memory, IOPS, and log disk specifications. Values that are not modified remain unchanged.

1. Log in to the sys tenant of the cluster as the root user.

2. Modify the resource specification.

   The statement is as follows:

   ALTER RESOURCE UNIT unitname 
   MAX_CPU [=] cpunum, 
   [MIN_CPU [=] cpunum,]
   MEMORY_SIZE [=] memsize, 
   [MAX_IOPS [=] iopsnum, MIN_IOPS [=] iopsnum,IOPS_WEIGHT [=]iopsweight,]
   [LOG_DISK_SIZE [=] logdisksize];
   

   Example: Modify the resource unit unit1:

   obclient> ALTER RESOURCE UNIT unit1 MAX_CPU 15, MEMORY_SIZE '20G', LOG_DISK_SIZE '4G';