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    PolarDB:Add a read-only IMCI node

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    PolarDB:Add a read-only IMCI node

    Last Updated:Jun 21, 2026

    This topic describes how to add a Read-only IMCI Node in the PolarDB console. Before you start, review the version requirements and precautions for columnstore indexes.

    Version requirements

    • For an Enterprise Edition cluster, the kernel version must be one of the following:

      • MySQL 8.0.1 with a revision version of 8.0.1.1.22 or later.

      • MySQL 8.0.2 with a revision version of 8.0.2.2.12 or later.

    • For a Standard Edition cluster that uses an x86 CPU architecture, the kernel version must be one of the following:

      • MySQL 8.0.1 with a revision version of 8.0.1.1.38 or later.

      • MySQL 8.0.2 with a revision version of 8.0.2.2.19 or later.

    Precautions

    • Your cluster must have at least one read-only node. You cannot add a read-only IMCI node to a single-node cluster.

    • For a multi-master cluster (Limitless), you must change the cluster parameter loose_polar_enable_imci_with_mm to ON to add a global read-only IMCI node.

    • For a cluster in a global database network (GDN), the loose_polar_enable_imci_with_standby cluster parameter must be enabled. The cluster must also meet one of the following conditions:

      • MySQL 8.0.1 with a revision version of 8.0.1.1.48 or later.

      • MySQL 8.0.2 with a revision version of 8.0.2.2.27 or later.

    • If there are usage limitations for columnar statements, the system automatically falls back to row-based execution.

    • The In-Memory Columnar Index (IMCI) feature and the failover with hot replica feature are mutually exclusive on some kernel versions.

      • For clusters with a kernel version of 8.0.1.1.43 or later or 8.0.2.2.24 or later, the IMCI feature is fully compatible with the failover with hot replica feature.

      • For clusters with a kernel version of 8.0.1.1.42 or 8.0.2.2.23:

        • If the cluster already has a read-only node with the failover with hot replica feature enabled, you can add a read-only IMCI node to the cluster.

        • If the cluster already has a read-only IMCI node, you cannot enable the failover with hot replica feature for any read-only node in the cluster.

      • For clusters with a kernel version earlier than 8.0.1.1.42 or 8.0.2.2.23, the IMCI feature and the failover with hot replica feature are mutually exclusive:

        • If the cluster already has a read-only node with the failover with hot replica feature enabled, you cannot add a read-only IMCI node to the cluster.

          Note

          If you want to add a read-only IMCI node to the cluster, you can contact us to disable the Voting Disk high-availability module for the failover with hot replica feature. After the module is disabled, you can add the read-only IMCI node. Note that all nodes are automatically restarted during this process.

        • If the cluster already has a read-only IMCI node, you cannot enable the failover with hot replica feature for any read-only node in the cluster.

    Procedure

    You can add a read-only IMCI node by using one of the following methods:

    Console

    1. Log on to the PolarDB console and select your cluster's region. Open the Add/Remove Node wizard in one of the following ways:

      • On the Clusters page, click Add/Remove Node in the Actions column.

      • On the Basic Information page of the target cluster, click Add/Remove Node in the Database Nodes section.

    2. Select Add Read-only IMCI Node and click OK.

    3. Add the read-only IMCI node and complete the payment.

      1. Click +Add a Read-only IMCI Node and select the node specifications.

      2. Select a switchover time.

      3. (Optional) Review the product terms of service and service level agreement.

      4. Click Buy Now.

    4. After you complete the payment, return to the cluster details page and wait for the read-only IMCI node to be added. The node is added when its status changes to Running. The Database Nodes section then displays the primary node, read-only node (hot replica), and read-only IMCI node, all with a status of Running.

    Results

    Go to the PolarDB console, find the target cluster, and navigate to its Basic Information page to verify that the read-only IMCI node was added.

    After the node is added, the Read-only IMCI Node is the newly added columnar storage node, and the Read-only Node is the original Read-only Node.

    Related APIs

    API

    Description

    CreateDBNodes

    Adds one or more read-only nodes to a PolarDB cluster.