FAQ

This topic summarizes the questions that are frequently asked during upgrades of OceanBase Migration Service (OMS) Community Edition.

What versions of OMS Community Edition can be upgraded to V4.2.3?

Only OMS Community Edition V4.1.0 and V4.2.2 can be directly upgraded to OMS Community Edition V4.2.3.

To upgrade OMS Community Edition of a version earlier than V4.1.0, you must upgrade it first to V4.1.0 and then to V4.2.3.

Must I back up the original database before the upgrade?

We recommend that you back up the original database before you start the upgrade. The backup of the original database is a fail-safe measure in the upgrade process. If the upgrade fails, you can promptly start the container of OMS Community Edition of the original version.

If you do not back up the original database, make sure that the name of the new database is the same as that of the original database. In addition, you cannot roll back to the original database if the upgrade fails.

How can I control the interval for pulling data from the store component?

You can enable high availability (HA) to automatically create a new store. The prerequisite for automatic store creation is that the number of stores under the subtopic does not exceed the value of the subtopicStoreNumberThreshold parameter of ha.config. By default, the number of stores under a subtopic is 5.

1. Log on to the console of OMS Community Edition.

2. In the left-side navigation pane, choose System Management > System Parameters.

3. On the System Parameters page, find ha.config and click the edit icon in the Value column.

4. In the Modify Value dialog box, set enable to true to enable HA.

5. Set the perceiveStoreClientCheckpoint parameter to true to enable data pulling from the store component for the downstream component.

   If you set perceiveStoreClientCheckpoint to false, you need to set the refetchStoreIntervalMin parameter to the desired value. This parameter specifies the time interval, in minutes, for pulling data from the store component.

   For example, if the tasks monitored in the original container are all executed in real time, you plan to stop the original container at 4:00 pm, and the upgrade is expected to complete at 5:00 pm, we recommend that you set the refetchStoreIntervalMin parameter to 90 minutes. This interval is the sum of a 60-minute period (between the container stop time and the upgrade end time) and a 30-minute redundant period (based on the business traffic).

If I modify the parameters of some processes before the upgrade, do the parameters exist after the upgrade?

• If you modify the parameters of the Full-Import, Incr-Sync, or Full-Verification component, the modified parameters still exist after the upgrade.

• If you modify the parameters of the store component, such as an allowlist-related parameter, the subtopic configuration is updated accordingly, and the modified parameters still exist after the upgrade succeeds.

Common issues in the upgrade from V4.1.0 to V4.2.3

• What can I do if I start an extra Store component in a data synchronization project?

  To avoid a waste of resources, you can suspend the extra Store component on the View Component Monitoring page of the data synchronization project. You can also log on to the OMS console, choose OPS & Monitoring > Components to manage Store components.

• What can I do if the following error about the Incr-Sync component is reported when a data migration project is running: com.oceanbase.oms.store.client.HttpBadResponseException: java.lang.RuntimeException: no active store under MYSQL_p_5****_reverse?

  The Incr-Sync component and the Store component are created at the same time in a data migration project, and the Incr-Sync component requires the Store component to write data. If the Incr-Sync component starts before the dependent Store component does, this error is reported.

  To solve this issue, perform the following steps:

  1. Go to the details page of the data migration project.

  2. Click View Component Monitoring in the upper-right corner.

  3. In the View Component Monitoring panel, find the Incr-Sync component and click Start in the Actions column.

• What can I do if neither the destination Store component nor the destination Incr-Sync component is started in a reverse incremental migration task of a data migration project?

  Solution 1:

  1. Go to the details page of the data migration project.

  2. Click the Forward Switchover tab to enter the forward switchover stage.

  3. In the Start Sink Store step, click Retry under Failed to start the destination Store.

  4. When the destination Store component starts, restart the reverse incremental migration task.

  Solution 2:

  If the preceding retry operation is not supported on the Forward Switchover tab, you can start the component by modifying the parameters of the rm database of OMS Community Edition.

  1. Query the rm database of OMS Community Edition.

     SELECT * FROM oms_step WHERE project_id = ' project ID';
     

  2. Query the ID of the task group whose step_name value is TRANSFER_APP_SWITCH.

  3. Query the oms_task table by using the obtained ID.

     SELECT * FROM oms_task WHERE task_group= 'id'
     

     In the query result, focus on the two records where the values of task_type are CREATE_DEST_STORE and CREATE_REVERSE_SYNC, which indicate the tasks for the destination Store component and destination Incr-Sync component.

  4. Find the task whose task_type is CREATE_DEST_STORE and change the value of task_status to PENDING to start the destination Store component.

     Check whether the value of retry_count is greater than the value of max_retry_count, whose default value is 3. If yes, a retry cannot be automatically triggered and you can change the value of retry_count to 0.

     After the background scheduling is completed, the value of task_status of CREATE_DEST_STORE becomes FINISHED. You can check whether the destination Store component is started on the View Component Monitoring tab of the project.

  5. Find the task whose task_type is CREATE_REVERSE_SYNC and change the value of task_status to PENDING to start the destination Incr-Sync component.

     After the background scheduling is completed, you can check whether the destination Incr-Sync component is started on the View Component Monitoring tab of the project.

• What can I do if the Store component or the Incr-Sync component is not started during the incremental synchronization stage of a data migration project?

  You can start the components by modifying parameters of the rm database of the OMS Community Edition.

  1. Query the rm database of OMS Community Edition.

     SELECT * FROM oms_step WHERE project_id = ' project ID';
     

  2. Find the task whose step_name is TRANSFER_INCR_LOG_PULL and change the value of step_status to FAILED and that of step_info to {}.

  3. After the background scheduling is completed, the value of task_status of TRANSFER_INCR_LOG_PULL becomes FINISHED. You can view information of the destination Store component on the View Component Monitoring tab of the project.

  4. Query the rm database of the OMS Community Edition again.

     SELECT * FROM oms_step WHERE project_id = ' project ID';
     

  5. Find the task whose step_name is INCR_TRANSFER and change the value of step_status to FAILED and that of step_info to {}.

  6. After the background scheduling is completed, the value of task_status of INCR_TRANSFER becomes MONITORING. You can view information of the destination Incr-Sync component on the View Component Monitoring tab of the project.