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    ApsaraDB RDS:Modify read weight distribution

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    ApsaraDB RDS:Modify read weight distribution

    Last Updated:Jun 20, 2026

    During peak business hours or in high-concurrency read scenarios, you can modify the read weights for a read-only routing endpoint. The endpoint then automatically forwards read requests to the secondary node and all configured read-only instances based on the new weights. This helps the read/write splitting service adapt to different business requirements and load conditions.

    Prerequisites

    The primary RDS for SQL Server instance must meet the following requirements. You can view this information on the Basic Information page of your instance.

    • Engine Version: 2017 RDS Cluster Edition, 2019 RDS Cluster Edition, 2022 RDS Cluster Edition, or 2025 RDS Cluster Edition

    • Instance Series: RDS Cluster Edition

    • Storage Type: ESSD

    • Billing Method: subscription or pay-as-you-go. Serverless instances are not supported.

    Procedure

    1. Log on to the ApsaraDB RDS console and go to the Instances page. In the top navigation bar, select the region in which the RDS instance resides. Then, find the RDS instance and click the instance ID.

    2. In the navigation pane on the left, click Cluster Management.

    3. Click Configure Readonly Splitting Address . In the dialog box, select Customized Distribution and set a read weight for each node. For example, set the read weight for the primary node to 0 and for the secondary node to 800.

      The higher the read weight of an instance, the more read requests it processes. For example, if a primary instance has three read-only instances with read weights of 100, 200, and 200, the read requests are distributed among the instances at a 1:2:2 ratio.

      • Automatic Distribution: The system automatically allocates the read weight of each instance based on its specifications. New read-only instances added to the primary instance are also automatically included in the read/write splitting link with system-allocated weights, requiring no manual setup. For more information, see System weight allocation rules.

      • Customized Distribution: Manually set the read weight for each instance. The value must be an integer from 0 to 10,000. If you add a read-only instance to the primary instance, its read weight defaults to 0 and must be modified manually.

      Note

      If a read-only instance is deleted, its weight is automatically removed. The weights of the other instances remain unchanged.

    4. Click OK.

    Related topics

    • If you use RDS Cluster Edition, secondary nodes in your RDS cluster are readable. An RDS instance that runs RDS Cluster Edition is referred to as an RDS cluster. After you create an RDS cluster, the secondary nodes in the RDS cluster serve as read-only nodes by default. For more information, see Readable secondary instance.

    • If you no longer need the read/write splitting feature, you can disable it. For more information, see Disable read/write splitting (read-only routing endpoint).