Dameng Migration Synchronization to Dameng

NineData data replication supports replicating data from Dameng to Dameng, including structure replication, full replication, and incremental replication.

Feature Introduction

NineData data replication supports high-performance replication of structure, full data, and incremental data between data sources. For certain data sources, it also provides bidirectional replication, enabling the quick construction of geo-distributed active-active business architectures.

• Structure: Supports the replication of object structures between homogeneous and heterogeneous data sources, greatly reducing the barrier to data replication between two sources.
• Full Data: Achieves row-level concurrent batch replication through intelligent data sharding, effectively ensuring replication performance. The independently developed novel breakpoint resume technology ensures the accuracy of data in tables without primary keys.
• Incremental Data: Supports DML and DDL incremental data replication for all object types. By leveraging technologies such as row-level concurrency and hotspot merging, it delivers robust replication performance.
• Bidirectional Real-time Data Replication (only between MySQL instances): Direct bidirectional replication of data between multiple nodes ensures that all node data remains up-to-date.

With the above features, it is easy and efficient to achieve scenarios such as full|incremental data replication, full|incremental data migration, full|incremental data synchronization, data integration, and seamless migration without downtime, providing enterprises with flexible and reliable data replication solutions.

Prerequisites

• The source and target data sources have been added to NineData. To add a Dameng data source, see Creating Dameng Data Source.

• Both the source and target data sources are Dameng.

• You have the following permissions for the source and target data sources:

  Replication Type	Source Data Source	Target Data Source
  Structure Replication	Read permissions on the objects to be replicated, and permissions to read system dictionaries and metadata	DDL
  Full Replication	Read permissions on the objects to be replicated, and permissions to read system dictionaries and metadata	TABLE-related permissions (ALTER, DROP, SELECT, INSERT, UPDATE, DELETE)
  Incremental Replication	Read permissions on the objects to be replicated, permissions to read system dictionaries and metadata, and permissions required to read incremental logs	TABLE-related permissions (ALTER, DROP, SELECT, INSERT, UPDATE, DELETE)

• For incremental replication, make sure archive logs or the configurations required for incremental log reading are enabled in the source Dameng database, and retain enough log files. For configuration details, refer to the Dameng official documentation or ask your database administrator to complete the configuration.

Usage Limitations

• Before data synchronization, assess the performance of the source and target data sources, and perform data synchronization during off-peak hours. Otherwise, full data initialization will consume read and write resources on both data sources and increase database load.
• Make sure each table in the synchronization objects has a primary key or unique constraint, and that column names are unique. Otherwise, the same data may be synchronized repeatedly.

Operation Steps

Commercialization Notice

NineData’s data replication product has been commercialized. You can still use 10 replication tasks for free, with the following considerations:

• Among the 10 replication tasks, you can include 1 Incremental task, with a specification of Micro.

• Tasks with a status of Terminated do not count towards the 10-task limit. If you have already created 10 replication tasks and want to create more, you can terminate previous replication tasks and then create new ones.

• When creating replication tasks, you can only select the Spec you have purchased. Specifications that have not been purchased will be grayed out and cannot be selected. If you need to purchase additional specifications, please contact us through the customer service icon at the bottom right of the page.

1. Log in to the NineData Console.

2. In the left navigation pane, click Replication > Data Replication.

3. On the Replication page, click Create Replication in the upper-right corner.

4. On the Source & Target tab, configure the parameters in the following table, and click Next.

   Parameter	Description
   Name	Enter a name for the data synchronization task. To make the task easier to find and manage later, use a meaningful name. Up to 64 characters are supported.
   Source	The data source that contains the objects to synchronize.
   Target	The data source that receives the synchronized objects.
   Target Object Name	Select the case conversion rule for object names after they are migrated from the source to the target. Convert all to Lowercase: Regardless of the naming rule on the source, all target names are lowercase. Consistent with Source: Keep the naming rule of the source. Convert all to Uppercase: Regardless of the naming rule on the source, all target names are uppercase.
   Type	Select the replication type. Schema: Synchronize only the database and table schemas of the source data source, without synchronizing data. Full: Synchronize all objects and data from the source data source, namely full data replication. Incremental: After full synchronization is complete, perform incremental synchronization based on the logs of the source data source.
   Incremental Started	Required only when Type is Incremental. From Started: Use the current replication task start time as the baseline for incremental replication. Customized Time: Select the point in time from which incremental replication starts. You can select a time zone based on the region of your business. If the configured time point is earlier than the current replication task start time and DDL operations occurred during that period, the replication task will fail.
   Spec	The specification of the replication task. A larger specification provides a higher replication rate. Hover over the icon to view the rate and configuration information of each specification. If you configure the data replication task before purchasing resources, you can select the required specification here. If you purchase resources before configuring the task, the system selects the specification chosen during resource purchase, and you cannot change it in the task configuration.
   If target table already exists (Required when Schema is selected)	Pre-Check Error and Stop Task: Stop the task when a table with the same name is detected during the precheck stage. Skip and Continue Task: When a table with the same name is detected during the precheck stage, display a prompt and continue the task. During schema replication, ignore the table with the same name. If you also perform data replication, data is appended to the table with the same name and existing data is not overwritten. Delete Objects and Rewrite: When a table with the same name is detected during the precheck stage, display a prompt and continue the task. During schema replication, delete the table with the same name in the target database and replicate the table schema again based on the source database. If you also perform data replication, data is written after schema replication is complete.
   Target Table Exists Data (Required when Full is selected)	Pre-Check Error and Stop Task: Stop the task when data is detected in the target table during the precheck stage. Ignore existing target data and append to it.: When data is detected in the target table during the precheck stage, ignore that data and append other data. Clear target existing data before write: When data is detected in the target table during the precheck stage, delete that data and write it again.
   Incremental data conflict handling strategy for target table (Required when Incremental is selected)	Runtime error: During incremental replication, report an error when target data already exists and wait for manual intervention. Do not update target data: During incremental replication, do not write data when target data already exists, and continue subsequent tasks. Update target data: During incremental replication, overwrite the target data when target data already exists.

5. On the Objects tab, configure the following parameters, and click Next.

   Parameter	Description
   Replication Objects	Select the content to replicate. You can select All Objects to replicate all content in the source database, or select Customized Object, select the content to replicate in the Source Object list, and click > to add it to the Target Object list on the right.

   If you need to create multiple replication links with the same replication objects, you can create a configuration file and import it when creating a task. Click Import Config in the upper-right corner, click Download Template to download the configuration file template, edit the file, and then click Upload to upload it for batch import. Configuration file description:

   Parameter	Description
   source_table_name	The source table name of the object to synchronize.
   destination_table_name	The target table name that receives the synchronized object.
   source_schema_name	The source schema name of the object to synchronize.
   destination_schema_name	The target schema name that receives the synchronized object.
   source_database_name	The source database name of the object to synchronize.
   target_database_name	The target database name that receives the synchronized object.
   column_list	The list of columns to synchronize.
   extra_configuration	Additional configuration information. You can configure the following information here: column_rules: Defines column mappings and value rules. Field descriptions: column_name: Original column name. destination_column_name: Specifies the target column name. column_value: Specifies the column value, which can be an SQL function or a constant value. filter_condition: Specifies row-level data filtering conditions. Only rows that meet the conditions are replicated.

   tip

   • The following is an example of extra_configuration:

     {
       "extra_config":{
         "column_rules":[
           {
             "column_name": "created_time", // Specifies the original column name to be mapped.
             "destination_column_name": "migrated_time", // Maps the target column name to "migrated_time".
             "column_value": "current_timestamp()" // Changes the column value to the current timestamp.
           }
         ],
         "filter_condition": "id != 0" // Only rows whose ID is not 0 are synchronized.
       }
     }

   • For a complete example of the configuration file, see the downloaded template.

6. On the "Mapping" tab, choose different operations based on the selected replication type, and click Save and Pre-Check. If the source and target data sources are updated during mapping configuration, click Refresh Metadata in the upper-right corner of the page to refresh the source and target data source information.

   • Includes Schema: Configure the table name after synchronization to the target data source.

   • Does not include Schema: The system selects the database with the same name in the target data source by default. If no such database exists, you need to manually select the target database. The table names and column names in the target database must match the synchronization objects. If they do not match, you can manually map the table names and column names.

   You can also perform the following operations:

   • Click Mapping & Filtering on the right side of the page to customize the column names after synchronization to the target data source.
   • On the Mapping & Filtering page, enter a comparison expression in the text box below Data Filter as the filtering condition. Only data that meets the filtering condition is synchronized to the target data source. For example, if the filtering condition is set to emp_no>=10005, data whose emp_no column value is less than 10005 is not synchronized to the target data source.
   • Click the icon to the right of "Target Table" to search for a table name and replace it with the target name.
   • Enter a table name in the Search Table text box in the upper-right corner to quickly locate the target table.
   • Click Batch Configuration in the upper-right corner to define common rules in batches, such as table name and column name case conversion, prefix or suffix addition, and replacement, so that mapping configuration can be applied uniformly to a large number of tables and columns.

7. On the Pre-check tab, wait for the system to complete the precheck. After the precheck is passed, click Launch.

   • You can select Enable data consistency comparison. After the synchronization task is complete, a data consistency comparison task based on the source data source automatically starts to ensure data consistency between both ends. Based on the selected Type, Enable data consistency comparison starts at the following times:

     • Schema: Starts after schema replication is complete.
     • Schema+Full: Starts after full replication is complete.
     • Full: Starts after full replication is complete.
     • Schema+Full+Incremental, Incremental: Starts when incremental data is consistent with the source data source for the first time and Delay is 0 seconds. You can click View Details and view the synchronization delay on the Details page.

   • If the precheck fails, click Details in the Actions column on the right of the failed check item, troubleshoot the cause, manually fix the issue, and then click Check Again to run the precheck again until it passes.

   • Check items whose Result is Warning can be fixed or ignored depending on the situation.

8. On the Launch page, the Launch Successfully prompt appears, indicating that the synchronization task has started. You can then perform the following operations:

   • Click View Details to view the execution status of each stage of the synchronization task.

   • Click Back to list to return to the Replication task list page.

Viewing Synchronization Results

1. Log in to the NineData Console.

2. Click on Replication > Data Replication in the left navigation bar.

3. On the Replication page, click on the Task ID of the target synchronization task, the page details are as follows.

   

   Number	Function	Description
   1	Sync Delay	The data synchronization delay between the source data source and the target data source. 0 seconds means there is no delay between the two ends, at which point you can choose to switch the business to the target data source for smooth migration.
   2	Configure Alerts	After configuring alerts, the system will notify you in the way you choose when the task fails.
   3	More	Pause: Pause the task, only tasks with Running status are selectable. Duplicate: Create a new replication task with the same configuration as the current task. Terminate: End tasks that are unfinished or listening (i.e., in incremental synchronization). Once the task is terminated, it cannot be restarted, so please proceed with caution. If the synchronization objects contain triggers, a trigger replication option will pop up, please select as needed. Delete: Delete the task. Once the task is deleted, it cannot be recovered, so please proceed with caution.
   4	Structure Replication (displayed in scenarios involving structure replication)	Displays the progress and detailed information of structure replication. Click on Log on the right side of the page: View the execution logs of structure replication. Click on on the right side of the page: View the latest information. Click on View DDL in the Actions column on the right side of the target object in the list: View SQL playback.
   5	Full Replication (displayed in scenarios involving full replication)	Displays the progress and detailed information of full replication. Click on Monitor on the right side of the page: View various monitoring indicators during full replication. During full replication, you can also click on Flow Control Settings on the right side of the monitoring indicator page to limit the rate of writing to the target data source per second. The unit is rows/second. Click on Log on the right side of the page: View the execution logs of full replication. Click on on the right side of the page: View the latest information.
   6	Incremental Replication (displayed in scenarios involving incremental replication)	Displays various monitoring indicators of incremental replication. Click on View Threads on the right side of the page: View the operations currently being executed by the current replication task, including: Thread ID: Replication tasks are executed in multiple threads, displaying the current thread number in progress. Execute SQL: Details of the SQL statement currently being executed by the current thread. Response Time: The response time of the current thread. If this value increases, it indicates that the current thread may be stuck for some reason. Event Time: The timestamp when the current thread was started. Status: The status of the current thread. Click on Flow Control Settings on the right side of the page: Limit the rate of writing to the target data source per second. The unit is rows/second. Click on Log on the right side of the page: View the execution logs of incremental replication. Click on on the right side of the page: View the latest information.
   7	Modify Object	Displays the modification records of synchronization objects. Click on Modify Objects on the right side of the page to configure the synchronization objects. Click on on the right side of the page: View the latest information.
   8	Data Comparison	Displays the comparison results between the source data source and the target data source. If you have not enabled data comparison, please click on Enable Comparison on the page. Click on Re-compare on the right side of the page: Re-initiate the comparison between the current source and target data sources. Click on Stop on the right side of the page: After the comparison task starts, you can click this button to stop the comparison task immediately. Click on Log on the right side of the page: View the execution logs of consistency comparison. Click on Monitor (displayed only in data comparison): View the trend chart of RPS (records per second) comparison. Click on Details to view earlier records. Click on in the Actions column on the right side of the comparison list (displayed under the Data tab only in the case of inconsistency): View details of the comparison between the source and target sides. Click on in the Actions column on the right side of the comparison list (displayed only in the case of inconsistency): Generate change SQL. You can directly copy this SQL to the target data source to execute and modify the inconsistent content.
   9	Expand	Display detailed information of the current replication task. Common Options: Export table configuration: Export the current task's database and table configuration, allowing for quick import when creating a new replication task. This helps rapidly establish multiple replication links with the same replication objects. Alert Rules: Configure the alarm strategy for the current task.

Appendix: Pre-Check Item List

Check Item	Check Content
Source Data Source Connection Check	Check the gateway status of the source data source, instance reachability, and the accuracy of the username and password
Target Data Source Connection Check	Check the gateway status of the target data source, instance reachability, and the accuracy of the username and password
Source Database Permission Check	Check whether the account permissions of the source database meet the requirements
Target Database Permission Check	Check whether the account permissions of the target database meet the requirements
Target Database Same-Name Object Existence Check	Check whether the objects to be replicated already exist in the target database
Target Database Data Existence Check	Check whether data already exists in the objects to be replicated in the target database
Source Database Table Without Primary Key Check	Check whether the objects to be replicated contain tables without a primary key or unique key
Cyclic Replication Check	Check whether a replication loop exists
Source Database Incremental Log Configuration Check	Check whether the source database meets the requirements for incremental log reading
Source Database Log Retention Check	Check whether the source database log retention period meets incremental replication requirements

Related Documentation

• Data Replication Introduction
• Creating Dameng Data Source