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    PolarDB:Migration evaluation

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    PolarDB:Migration evaluation

    Last Updated:Apr 16, 2024

    The migration evaluation feature is provided by PolarDB to ensure the successful execution of migration tasks and high migration efficiency. This feature allows you to precheck the prerequisites such as the instance status, migration task dependencies, and attributes of the source instance before you upgrade an ApsaraDB RDS for MySQL instance to a PolarDB for MySQL cluster. This way, you can identify the factors that may affect the migration progress and resolve the issue in advance to reduce the processing and resource costs during migration.

    Supported regions

    The migration evaluation feature is available in the following regions:

    China (Hangzhou), China (Shanghai), China (Shenzhen), China (Beijing), China (Zhangjiakou), China (Ulanqab), China (Chengdu), China (Hong Kong), Singapore, Indonesia (Jakarta), US (Silicon Valley), and US (Virginia).

    Create a migration evaluation task

    1. Log on to the PolarDB console.

    2. Create a migration evaluation task. PolarDB provides three methods for creating an evaluation task:

      • From the Clusters page: Click Migration/Upgrade Evaluation in the upper-left corner of the Clusters page.

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      • From the Migration/Upgrade page: Click Migration/Upgrade Evaluation in the upper-left corner of the Migration/Upgrade page.

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      • From the PolarDB buy page: Select Migrate from RDS, set Source RDS Version, Database Engine, and Database Edition, and then click Migration Evaluation.

    3. Configure parameters for the migration evaluation task.

      Parameter

      Description

      Creation Method

      Select Migrate from RDS.

      If you create a migration evaluation task from the PolarDB buy page, you do not need to specify this parameter. Migrate from RDS is automatically selected.

      Source RDS Version

      The database engine version of the source ApsaraDB RDS instance.

      Source RDS Instance

      Select a source ApsaraDB RDS instance from the drop-down list.

      Destination Database Engine

      The database engine version of the destination PolarDB for MySQL cluster.

      Product Edition

      The edition of the destination PolarDB for MySQL cluster.

      Click Next.

    4. PolarDB prechecks and evaluates your source ApsaraDB RDS instance and migration plan in terms of Basic Information Verification, Migration Task Dependency Verification, Key Information Verification, and Other Verification. Handle the issues based on the evaluation results.

      Answers to some commonly asked questions about migration evaluation in PolarDB are provided in this topic. For more information, see FAQ.

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    5. Click Continue to Buy or Buy to go to the PolarDB buy page. For more information, see Procedure.

    Manage the migration evaluation task

    To view the details of the created evaluation task, go to the Migration/Evaluation page. If the evaluation task is complete, you can click Re-evaluate or Buy.

    Note

    The evaluation task is retained for seven days and then automatically deleted. If your evaluation task has expired, you can create an evaluation task.

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    FAQ

    Category

    Check item

    Solution

    Basic Information Verification

    Source Instance Running Status

    The source ApsaraDB RDS instance must be in the Running state.

    Source Instance Read/Write Status

    The source ApsaraDB RDS instance must be in the Running state and in Read/Write mode.

    Source Instance Account Mode

    If Database Proxy (Safe Mode) is enabled for the ApsaraDB RDS for MySQL instance, a privileged account is created or the network connection mode of the ApsaraDB RDS for MySQL instance is switched to high-performance mode. For more information, see Create an account and [Product changes/Feature changes] The network connection mode of an ApsaraDB RDS instance is upgraded.

    Service-linked Role for PolarDB

    The service-linked role for PolarDB is created for the account.

    For more information about how to create a PolarDB service-linked role, see Precheck whether the service-linked role for PolarDB is created. You can also create a PolarDB service-linked role by calling the API operation.

    Migration Task Dependency Verification

    DTS Permissions

    Your Alibaba Cloud account must have the permissions to access cloud resources over DTS.

    For more information, see Authorize DTS to access Alibaba Cloud resources.

    Whether Source Instance is Empty

    Databases are created in the source ApsaraDB RDS instance. You must create a database in the instance before you can migrate data.

    Source Instance Table Engine Verification

    The table storage engine for the source RDS instance must be InnoDB or X-Engine.

    Source Instance Trigger Verification

    If triggers are created for the source ApsaraDB RDS instance, delete the triggers first. Otherwise, the migration process will be interrupted.

    You can manually create triggers in the destination PolarDB cluster after the migration process is complete.

    Verification for Non-primary-key Tables in Source Instance

    If the source ApsaraDB RDS instance contains tables without primary keys, duplicate data may occur in the destination PolarDB cluster after data is synchronized.

    You can connect to the database on the source ApsaraDB RDS instance by using a privileged account and execute the following SQL statement to query tables without primary keys:

    SELECT t1.table_schema, t1.table_name 
FROM information_schema.TABLES t1 LEFT OUTER 
	JOIN information_schema.TABLE_CONSTRAINTS t2 
  ON t1.table_schema = t2.TABLE_SCHEMA AND t1.table_name = t2.TABLE_NAME AND t2.CONSTRAINT_NAME 
  IN ("PRIMARY") 
WHERE t2.table_name IS NULL AND t1.table_type = "BASE TABLE" AND t1.TABLE_SCHEMA NOT IN ("information_schema", "performance_schema", "mysql", "sys")

    You can add primary keys to the tables without primary keys.

    If you confirm that duplicate data is acceptable, you can ignore this evaluation result and select Continue when the error message is returned when you Upgrade an ApsaraDB RDS for MySQL instance to a PolarDB for MySQL cluster.

    Key Information Verification

    Source Instance Root Account Verification

    To ensure compatibility between ApsaraDB RDS for MySQL and PolarDB in terms of the system account structure and to prevent the system accounts of the destination PolarDB cluster from being overwritten during migration, make sure that the root and aliyun_root accounts do not exist in the source ApsaraDB for RDS instance at the same time. For more information, see Remove redundant system accounts from the source ApsaraDB for RDS instance.