• Document Database Service

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  2. Document Database Service
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  4. Getting Started
  5. Creating a Replica Set Instance

Creating a Replica Set Instance


This section describes how to create a DDS replica set instance on the DDS management console. DDS allows you to tailor your computing resources and storage space to your business needs.

You can use your account to create a maximum of 50 replica set instances in total. To create more replica set instances, click in the upper right corner of the management console. On the Service Quota page, click Increase Quota to apply for quotas.


  1. Log in to the management console.
  2. Click in the upper left corner and select a region and project.
  3. Click Service List. Under Database, click Document Database Service.
  4. On the Instance Management page, click Create DB Instance.
  5. On the displayed page, configure parameters about DB instance specifications. Then, click Create Now.

    Table 1 Basic information




    A region where the tenant is located. It can be changed in the upper left corner. For details, see section Regions and AZs.


    DB instances in different regions cannot communicate with each other through a private network and you cannot change the region of a DB instance after creating the instance. Therefore, exercise caution when selecting a region.

    Database Type

    Community Edition

    DB Instance Type

    Select Replica set.

    A replica set consists of the primary node, secondary node, and hidden node. If a primary node goes down or becomes faulty, a secondary node is automatically elected to the primary role and continues normal operation. If a secondary node is unavailable, a hidden node will take the role of the secondary to ensure high availability.

    DB Instance Name

    The DB instance name can be 4 to 64 characters long. It must start with a letter and can contain only uppercase letters, lowercase letters, digits, hyphens (-), and underscores (_). After the DB instance is created, you can change the instance name. For details, see section Modifying the DB Instance Name.

    Compatible MongoDB Version


    Storage Engine



    A physical region where resources use independent power supply and networks. AZs are physically isolated but interconnected through the internal network. For details, see section Regions and AZs.

    Disk Encryption

    • Disable: Disable the encryption function.
    • Enable: Enable the encryption function. This feature improves data security but negatively affects system performance.

      Key Name: Select or create a private key, which is the tenant key.

      • After a DB instance is created, the disk encryption status and the key cannot be changed. The backup data stored on OBS is not encrypted.
      • After a DB instance is created, do not disable or delete the key that is being used. Otherwise, DDS becomes unavailable and data cannot be restored.
      • For details about how to create a key, see the "Creating a CMK" section in the Key Management Service User Guide.
    Table 2 Specifications



    Node Class

    For details about the DB instance specifications, see section DB Instance Specifications.

    Storage Type

    Ultra-high I/O: uses the SSD disk type.

    Storage Space

    Ranges from 10 GB to 2,000 GB. The value must be a multiple of 10.

    Table 3 Network




    The VPC which a DB instance belongs to implements network isolation for different services. It allows user to manage and configure internal networks and change network configuration, simplifying network management. You need to create or select the required VPC. For details on how to create a VPC, see section "Creating a VPC" in the Virtual Private Cloud User Guide.


    A subnet provides dedicated network resources that are logically isolated from other networks, improving network security.

    Security Group

    A security group control access to enhance security when DDS and other services access each other.


    Ensure that the security group rule you set allows clients to access DB instances. For example, select the TCP protocol with inbound direction, input the default port number 8635, and enter a subnet IP address or select a security group that the DB instance belongs to.

    Table 4 Database configuration




    The default account is rwuser.

    Administrator Password

    The password is a string of 8 to 32 characters. It must be a combination of uppercase letters, lowercase letters, digits, and special characters. You can also use the following special characters: ~!@#%^*-_=+?

    The system cannot save you password. Keep the password secure.

    Confirm Password

    The value of this parameter must be the same as the Administrator Password.


    Secure Sockets Layer (SSL) certificates set up encrypted connections between clients and servers, preventing data from being tampered with or stolen during transmission.

    SSL is enabled by default. After the DB instance is created, you can connect to the instance using SSL. For details, see section Connecting to a DB Instance.

    Table 5 Tag




    Tags a DDS DB instance. This configuration is optional. Adding tags to DDS DB instances helps you better identify and manage them. A maximum of 10 tags can be added for a DB instance.

    A tag is composed of a key-value pair.

    • Key: Mandatory if the DB instance is going to be tagged
      • For each DB instance, each tag key is unique.
      • A tag key consists of a maximum of 36 characters.
      • The key can only consist of digits, letters, underscores (_), and hyphens (-).
    • Value: Optional if the DB instance is going to be tagged
      • The value consists of a maximum of 43 characters.
      • The value can only consist of digits, letters, underscores (_), and hyphens (-).

    After a DB instance is created, you can view its tag details on the Tags tab. In addition, you can add, modify, and delete tags for existing DB instances. For details, see Tag.


    The performance of your DB instance is determined by how you configure it during the creation. The hardware configuration items that can be selected include the class and storage space of the replica set.

  6. On the displayed page, confirm your specifications.

    • If you need to modify your settings, click Previous to modify DB instance information.
    • If you do not need to modify your settings, click Submit to complete the DB instance application.

  7. After a DDS DB instance is created, you can view and manage it on the Replica Sets tab on the Instance Management page.

    • When a DB instance is being created, the status displayed in the Status column is Creating. This process takes about 15 minutes. After the creation is complete, the status changes to Available.
    • DDS enables the automated backup policy by default. After a DB instance is created, you can modify or disable the automated backup policy. An automated full backup is immediately triggered after the creation of a DB instance.
    • You can change the database port after the DB instance is created. DDS uses port 8635 by default, which is different from the default port numbers used by databases. To ensure database accessibility, you need to add the required security group rule.
    • After a DB instance is created, the system selects a parameter group that matches the replica set by default.