ApsaraDB for MongoDB:Change the configurations of a replica set instance

Billing rules

For more information, see Configuration change fees.

Limits

• If the instance uses the Classic Network, you must enable public access or switch to a virtual private cloud (VPC) to change the number of Read-only Nodes.

• You cannot reduce the storage space of an instance when you change its configurations. To reduce the storage space, you must create a new instance to replace the original one. For more information, see Other configuration change scenarios and methods.

• You cannot change the instance type or storage class when you change configurations. For example, you cannot change a replica set instance to a sharded cluster instance. To change the instance type or storage class, you must create a new instance to replace the original one. For more information, see Other configuration change scenarios and methods.

Usage notes

• The time required to complete a configuration change depends on factors such as network conditions, the task queue, and the data volume. Change the instance configurations during off-peak hours and ensure that your application has an automatic reconnection mechanism.

• For general-purpose or dedicated instances with local disks, if you only scale out storage and the host physical machines have sufficient resources, the scale-out is performed locally without a migration or switchover. The change takes effect immediately without connection interruptions, regardless of the selected switch time.

• For instances that use cloud disks, if you only scale out the storage space, the configuration change takes effect immediately. This process does not cause connection interruptions, regardless of the selected switchover time.

• During a configuration change, one or two transient connections may occur, each lasting for approximately 30 seconds. Set the Switching Time to an off-peak period to specify when the configuration change takes effect and to prevent service interruptions.

• Configuration changes do not cause data loss.

• When you change the configurations of an instance that uses local disks, the system, by default, upgrades the minor database version to the latest version.

Procedure

1. Go to the MongoDB replica set instances page. At the top of the page, select a resource group and a region. Then, click the ID of the target instance.

2. In the Specification Information section, follow the appropriate step for your instance's billing method to navigate to the configuration change page.

   • Subscription instance

     In the upper-right corner of the Specification Information section, click Upgrade or Downgrade.

   • Pay-as-you-go instance

     In the upper-right corner of the Specification Information section, click Change Configurations.

3. On the configuration change page, set the following parameters.

   Change Type	Parameter	Description
   Upgrade Configuration Downgrade Configuration	Active-standby Nodes	Select the number of primary and secondary nodes. Valid values: Three Nodes Replicaset: Downgrade is not supported. Five Nodes Replicaset: Can be downgraded to Three Nodes Replicaset . Seven Nodes Replicaset: Can be downgraded to Three Nodes Replicaset or Five Nodes Replicaset.
   	Read-only Nodes	Select the number of read-only nodes. The value must be an integer from 0 to 5.
   	Specifications	Select the target specifications. For more information about the specifications available for replica set instances, see Instance types.
   	Storage	Select the new storage space. Note You cannot reduce the storage space of an instance when you change its configurations. To reduce the storage space, you must create a new instance to replace the original one. For more information, see Other configuration change scenarios and methods. The storage space that you select is for each node, not the total storage space of all nodes.
   	Switching Time	Select when the configuration change takes effect. Switch Immediately After Data Migration: The system applies the change immediately after data migration is complete. Switch Within Maintenance Window: The system applies the change within the specified maintenance window. You can use the current maintenance window or set a new one. Click Modify next to Switch Within Maintenance Window. In the Specification Information section, click Edit next to Maintenance Window to set the switchover time. For more information, see Set a maintenance window. Note For general-purpose or dedicated instances with local disks, if you only scale out storage and the host physical machines have sufficient resources, the scale-out is performed locally without a migration or switchover. The change takes effect immediately without connection interruptions, regardless of the selected switch time. For instances that use cloud disks, if you only scale out the storage space, the configuration change takes effect immediately. This process does not cause connection interruptions, regardless of the selected switchover time.

4. Read the Terms of Service, click Buy Now, and then complete the payment as prompted.

   When you change the configurations of the instance, the instance status is Changing Configuration. If the instance status changes to Running, the instance configurations are changed.

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