Oracle to MySQL Data Replication

NineData Data Replication supports schema replication, full replication, and incremental replication from Oracle to MySQL.

Overview

Use this workflow to move Oracle data into MySQL for migration, downstream applications, or ongoing synchronization.

NineData data replication supports schema, full data, and incremental data replication between data sources. For supported data sources, it also supports bidirectional replication for geo-distributed active-active architectures.

• Schema replication: Replicates object structures between homogeneous and heterogeneous data sources.
• Full data replication: Uses data sharding and row-level concurrent batch replication to improve throughput. Breakpoint resume helps preserve data accuracy, including for tables without primary keys.
• Incremental data replication: Replicates DML and DDL changes for supported object types. Row-level concurrency and hotspot merge processing help maintain replication throughput.
• Bidirectional real-time data replication (only between MySQL instances): Replicates changes in both directions between nodes so data can stay current across participating nodes.

Use these capabilities for full or incremental data replication, migration, synchronization, data integration, and low-downtime migration workflows.

Before you begin

• Add both data sources to NineData. For instructions, see Add Data Source.

• The source data source must be Oracle 23ai, 21c, 19c, 18c, 12c, or 11g.

• The target data source must be MySQL 8.0, 5.7, 5.6, or 5.5.

• Make sure the source and target accounts have the following permissions.

  Replication type	Source data source	Target data source
  Schema Replication	select connect select any dictionary select any table select_catalog_role	ALL Privileges ON database
  Full Replication	select connect select any dictionary select any table select_catalog_role	ALL Privileges ON database
  Incremental Replication	See Appendix 3: Oracle incremental replication account permissions in this document.	ALL Privileges ON database

• For incremental replication, configure the following settings on the source data source:

  • Set the Oracle log mode to ARCHIVELOG mode. The default is NOARCHIVELOG.

    To check the current log mode, run:

    SELECT log_mode FROM v$database;

    If the log mode is NOARCHIVELOG, run these commands:

    SHUTDOWN IMMEDIATE;
    STARTUP MOUNT;
    ALTER DATABASE ARCHIVELOG;
    ALTER DATABASE OPEN;

  • Enable supplemental logging. It is disabled by default.

    To check whether supplemental logging is enabled, run:

    SELECT supplemental_log_data_all allc FROM v$database;

    If the result is NO, use the command that applies to your scenario:

    ALTER DATABASE ADD SUPPLEMENTAL LOG DATA (ALL) COLUMNS;
    ALTER TABLE <database_name>.<table_name> ADD SUPPLEMENTAL LOG DATA (ALL) COLUMNS;
    ALTER DATABASE ADD SUPPLEMENTAL LOG DATA;

    ALTER DATABASE ADD SUPPLEMENTAL LOG DATA (ALL) COLUMNS enables database-level supplemental logging and can consume more resources. ALTER TABLE <database_name>.<table_name> ADD SUPPLEMENTAL LOG DATA (ALL) COLUMNS enables supplemental logging for a specific table.

Restrictions

• Check source and target performance before you start. Run the task during off-peak hours when possible because full initialization reads and writes both data sources and can increase load.
• Make sure each replicated table has a primary key or unique constraint, and that column names are unique. Otherwise, the same data may be copied more than once.

Procedure

1. Sign in to the NineData Console.

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

3. On the Replication page, click Create Replication.

4. On the Source & Target tab, configure the fields in the 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.
   Datahub Project	Select the target Datahub Project. Data from the source data source will be written to the specified Project.
   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.
   Replication Mode	Select the replication mode. Uni-directional: A unidirectional data replication task from the source data source to the target data source. Bi-directional: A bidirectional incremental data replication task between the source and target data sources.
   Type	Required when Replication Mode is Bi-directional.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. The switch on the right enables periodic full replication. For more information, see Periodic Full Replication. Incremental: After full synchronization is complete, perform incremental synchronization based on the logs of the source data source.The icon is used to configure incremental operation types. You can clear specific operation types as needed. Cleared operation types will be ignored during incremental synchronization.
   Forward Type	Required when Replication Mode is Bi-directional. Select the forward 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.The icon is used to configure incremental operation types. You can clear specific operation types as needed. Cleared operation types will be ignored during incremental synchronization.
   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.
   Forward Incremental Started	Required only when Forward 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.
   Reverse Type	The replication type from the target data source to the source data source. This parameter is displayed only when Replication Mode is Bi-directional. Only Incremental is supported, and it is selected by default and cannot be disabled.
   Spec (Unavailable only when Schema is selected)	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. Each specification shows the available quantity and total quantity. When the available quantity is 0, the specification is grayed out and cannot be selected.
   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 message 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 message 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 parameters in the table, and click Next.

   Parameter	Description

   To create multiple replication tasks with the same replication objects, import a configuration file. Click Import Config, click Download Template to download the template, edit the file, and then click Upload to upload it and import the objects in bulk. The configuration file uses these fields:

   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. This field supports: 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

   • Example of extra_configuration:

     {
       "extra_config":{
         "column_rules":[
           {
              "column_name": "created_time",
              "destination_column_name": "migrated_time",
              "column_value": "current_timestamp()"
           }
         ],
          "filter_condition": "id != 0"
       }
     }

     In this example, created_time is mapped to migrated_time, the target column value is changed to current_timestamp(), and only rows whose id value is not 0 are synchronized.

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

6. On the "Mapping" tab, configure the mapping that matches the selected replication type, then click Save and Pre-Check. If source or target metadata changes while you configure mappings, click Refresh Metadata to refresh the metadata.

   • 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, select the target database manually. The table names and column names in the target database must match the synchronization objects. If they do not match, map the table names and column names manually.

   You can also perform these actions:

   • Click Mapping & Filtering to customize the column names after synchronization to the target data source.
   • On the Mapping & Filtering page, click Data Filter to configure filtering conditions by using comparison expressions. Only data that meets the filtering conditions 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 to quickly locate the target table.
   • Click Batch Configuration to define common rules in batches, such as table name and column name case conversion, prefix or suffix addition, and replacement. Use this option to apply mapping configuration to many tables and columns at the same time.

You can also perform these actions:

• Click Mapping & Filtering to customize target column names after synchronization.
• 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 emp_no>=10005, data whose emp_no column value is less than 10005 is not synchronized to the target data source.
• Click the icon next to "Target Table" to search for table names and replace them with target names.
• Enter a table name in the Search Table text box to quickly locate the target table.
• Click Batch Configuration to define common rules in batches, such as table or column name case conversion, prefix or suffix addition, and replacement. Use batch rules to apply consistent mapping 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 passes, click Launch.

   • Select Enable data consistency comparison to start a data consistency comparison task based on the source data source after synchronization completes. Based on the selected Type, Enable data consistency comparison starts at these 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. Click View Details to view synchronization delay on the Details page.

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

   • Items with Warning in Result can be fixed or ignored as needed.

8. On the Launch page, the Launch Successfully message appears, indicating that the synchronization task has started. You can then perform these actions:

   • 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.

Result

1. Sign in to the NineData Console.

2. Go to Replication > Data Replication.

3. On the Replication page, click the Task ID of the target replication task. The page shows the following information.

   

   Number	Function	Description
   1	Synchronization Delay	The delay between the source and target data sources. A value of 0 seconds means there is no delay. At that point, switch business traffic to the target data source for a smooth cutover.
   2	Configure Alerts	Configure alerts to get task-failure notifications by the method you choose. For more information, see Maintenance and Monitoring Overview.
   3	More	Pause: Pause a task whose status is Running. Terminate: Terminate a task that is unfinished or still monitoring incremental changes. A terminated task cannot be restarted. Proceed with caution. If the synchronized objects include triggers, trigger replication options appear. Choose the option that matches your task. Delete: Delete the task. Deleted tasks cannot be recovered. Proceed with caution.
   4	Schema Replication (shown when schema replication is included)	Shows the progress and details of schema replication. Click Logs to view schema replication logs. Click to view the latest information. Click View DDL in the Operation column for the target object to view the SQL replay.
   5	Full Replication (shown when full replication is included)	Shows the progress and details of full replication. Click Monitoring to view full replication metrics. During full replication, click Rate Limit Settings to limit the write rate to the target data source. The unit is rows per second. Click Logs to view full replication logs. Click to view the latest information.
   6	Incremental Replication (shown when incremental replication is included)	Shows incremental replication metrics. Click View Threads to view the operations currently running in the replication task, including: Thread ID: The replication task runs in multiple threads. This shows the current thread number. Execute SQL: Details of the SQL statement the thread is currently running. Response Time: The current thread response time. If this value increases, the thread may be stuck. Event Time: The timestamp when the current thread started. Status: The current thread status. Click Rate Limit Settings to limit the write rate to the target data source. The unit is rows per second. Click Logs to view incremental replication logs. Click to view the latest information.
   7	Modify Object	Shows change records for synchronized objects. Click Modify Synchronized Objects to update synchronized objects. Click to view the latest information.
   8	Data Comparison	Shows the comparison results between the source and target data sources. If data comparison is not enabled, click Enable Data Comparison on the page. Click Recompare to compare the current source and target data again. Click the date to view all comparison result lists, then click a target list item to switch to that result's details. Click Logs to view consistency comparison logs. Click Monitoring to view the comparison RPS (records per second) trend chart. Click Details to view earlier records. Click in the Operation column of the comparison list (shown when there are differences) to view the detailed comparison between source and target. Click in the Operation column of the comparison list (shown when there are differences) to generate a change SQL statement. Copy it to the target data source and run it to fix the inconsistency.
   9	Expand	Shows detailed information about the current replication task, including Replication Type, Replication Objects, Start Time, and more.

Appendix 1: Oracle to MySQL data type mapping

During replication, Oracle data types are mapped to the corresponding MySQL data types.

Type	Oracle Data Type	MySQL Data Type
Built-in data type	CHAR [(size [BYTE | CHAR])]	VARCHAR[(size)]
	NCHAR[(size)]	VARCHAR[(size)]
	VARCHAR2(size [BYTE | CHAR])	VARCHAR[(size)]
	NVARCHAR2(size)	VARCHAR[(size)]
	CLOB	LONGTEXT
	NCLOB	LONGTEXT
	LONG	LONGTEXT
	NUMBER [ (p [, s]) ]	For whole numbers (NUMBER): If the length is less than 10: INT If the length is greater than or equal to 10 but less than 20: BIGINT If the length is greater than or equal to 20: DECIMAL For non-whole numbers (NUMBER): DECIMAL For NUMBER with the identity increment property: BIGINT
	FLOAT [(p)]	FLOAT [(p)]
	DATE	DATE
	BINARY_FLOAT	FLOAT
	BINARY_DOUBLE	FLOAT
	TIMESTAMP [(fractional_seconds_precision)]	DATETIME
	TIMESTAMP [(fractional_seconds_precision)] WITH TIME ZONE	TIMESTAMP
	TIMESTAMP [(fractional_seconds_precision)] WITH LOCAL TIME ZONE	TIMESTAMP
	INTERVAL YEAR [(year_precision)] TO MONTH	VARCHAR(32)
	INTERVAL DAY [(day_precision)] TO SECOND [(fractional_seconds_precision)]	VARCHAR(32)
	RAW(size)	VARBINARY(size)
	LONG RAW	LONGBLOB
	BLOB	LONGBLOB
Oracle supplied data type	AnyData	TEXT

Appendix 2: Precheck items

Check item	What NineData checks
Source data source connection check	Checks the source gateway status, instance accessibility, and username and password accuracy.
Target data source connection check	Checks the target gateway status, instance accessibility, and username and password accuracy.
Target database permission check	Checks whether the target database account permissions meet the requirements.
Source database permission check	Checks whether the source database account permissions meet the requirements.
Target data source trigger check	Checks whether triggers exist in the target database.
Target database data existence check	Checks whether the objects to be replicated already have data in the target database.
Target database same-name object existence check	Checks whether the objects to be replicated already exist in the target database.
Source database log archiving mode check	Checks whether the source database log archiving mode is ARCHIVELOG.
Source database supplemental logging check	Checks whether source database supplemental logging is enabled and set to ALL.

Appendix 3: Oracle incremental replication account permissions

Below Oracle 12c

Designate a user with DBA privileges for incremental data replication tasks with Oracle as the source.

-- Create NineData sync account
CREATE USER test_dba IDENTIFIED BY "ninedatasync";
-- Grant DBA privileges to the account
GRANT dba to test_dba;

Oracle 12c and above

Designate a user with DBA privileges for incremental data replication tasks with Oracle as the source.

-- Create NineData sync account in the global environment
CREATE USER c##test_dba IDENTIFIED BY "ninedatasync";
-- Grant DBA and connect privileges to the account, specifying the scope of the privileges
GRANT dba, connect to c##nine_data container=all;

Next steps

• Data Replication overview