Oracle Replication to MySQL

NineData data replication supports data synchronization from Oracle to MySQL data sources.

Prerequisites

Ensure that both the source and target data sources have been added to NineData. For instructions on how to add them, please refer to Adding Data Sources.
The source data source should be Oracle, with a version of 23c, 21c, 19c, 18c, 12c, or 11g.
The target data source should be MySQL, with a version of 8.0, 5.7, 5.6, or 5.5.

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

Replication Type	Source Data Source	Target Data Source
Structure Replication	select connect select any dictionary select_catalog_role	ALL Privileges ON database
Full Replication	select connect select any dictionary select_catalog_role	ALL Privileges ON database
Incremental Replication	select connect select any dictionary select_catalog_role execute_catalog_role	ALL Privileges ON database

If incremental replication is needed, ensure that the following configurations are done in the source data source:

Set Oracle's log mode to ARCHIVELOG mode (default is NOARCHIVELOG).

sqlCopy code
Verify the current log mode: SELECT log_mode FROM v$database;
If the log mode is NOARCHIVELOG, perform the following steps:
1. Shut down the database: SHUTDOWN IMMEDIATE;
2. Start and mount the database: STARTUP MOUNT;
3. Execute the archive log opening command: ALTER DATABASE ARCHIVELOG;
4. Start the database: ALTER DATABASE OPEN;

Ensure that Supplemental Log, i.e., additional logs, is enabled (not enabled by default).

sqlCopy code
Verify if supplemental log is enabled: SELECT supplemental_log_data_all allc FROM v$database;
If it returns NO, execute the command to enable supplemental log:
- ALTER DATABASE ADD SUPPLEMENTAL LOG DATA (ALL) COLUMNS;
// Enables supplemental log at the database level, affecting all tables and columns, consuming more resources.
- ALTER TABLE <database_name>.<table_name> ADD SUPPLEMENTAL LOG DATA (ALL) COLUMNS;
// Enables supplemental log on a specific table, affecting all columns in that table.

Usage Restrictions

Evaluate the performance of both the source and target data sources before executing data synchronization. It is recommended to perform data synchronization during business off-peak hours. Otherwise, full data initialization will consume a certain amount of read-write resources from the source and target data sources, leading to an increase in database load.
Ensure that each table in the synchronized objects has a primary key or unique constraint, and column names are unique to avoid potential duplication of synchronized data.

Operation Steps

Log in to the NineData Console.
Click on in the left navigation bar.
On the page, click on the in the top right corner.

On the tab, configure according to the table below, and click on .

Parameter	Description
	Enter the name of the data synchronization task. For easy retrieval and management, use a meaningful name, up to 64 characters.
	The data source where the sync object is located.
	The data source that receives the sync object.
	Choose the content to be copied to the target data source. : Only syncs the table structure of the source data source, without syncing data. : Syncs all objects and data from the source data source, i.e., full data replication. The switch on the right is for toggling periodic full replication. For more information, please refer to Periodic Full Replication. : After full sync, perform incremental sync based on the log of the source data source. The icon represents incremental operation type configuration (not supported by some replication links). You can deselect certain operation types as needed. Once deselected, these operations will be ignored during incremental synchronization.
	(selected when is selected) : Stop the task when a table with the same name is detected during precheck. : Send a prompt when a table with the same name is detected during precheck and continue the task. During structure replication, ignore this table with the same name. If you are also performing data replication, data will be appended to this table with the same name without overwriting existing data. : Send a prompt when a table with the same name is detected during precheck and continue the task. During structure replication, delete the table with the same name in the target database and replicate the table structure based on the source database. If you are also performing data replication, data will be written after the table structure replication is completed. (optional when performing both structure and data replication): Send a prompt when a table with the same name is detected during precheck and continue the task. During structure replication, keep the table structure in the target database and, when data replication starts, clear the data in the table with the same name and then replicate from the original table. (required when is not selected) : Stop the task when data exists in the target table during precheck. : Ignore this part of the data when data is detected in the target table during precheck and append other data. : Delete this part of the data when data is detected in the target table during precheck and rewrite it.

On the tab, configure the following parameters, and then click on .

Parameter	Description
	Choose what to copy. You can choose to copy all contents of the source database, or choose to select the contents to be copied in the list and click > to add them to the right list.

On the tab, select different actions based on the selected replication type. If updates occur in the source and target data sources during the configuration mapping phase, you can click the button in the upper right corner of the page to refresh the information of the source and target data sources.
- Includes : Configure the table name after the target table is synchronized to the target data source, and click .
  tip
  You can click on on the right side of the page to customize the name of the columns after synchronization to the target data source. In addition, you can set to configure filter conditions through comparison expressions. Only data that meets the filter conditions will be synchronized to the target data source. For example, setting the filter condition to emp_no>=10005 means that data with emp_no less than 10005 will not be synchronized to the target data source.
- Excludes : The system automatically selects the same name database in the target data source by default. If it does not exist, you need to manually select the target database. The table names and column names in the target database need to be consistent with the sync objects. If they are not consistent, you can manually map the table names and column names.
On the tab, wait for the system to complete the precheck. After the precheck passes, click on .
tip
- You can check . After the sync task is completed, automatically initiate data consistency comparison based on the source data source to ensure data consistency on both ends. Depending on your choice of , the timing of starting is as follows:
  - : Initiated after structure replication is completed.
  - + , : Initiated after full replication is completed.
  - + + , : Initiated when the incremental data is first consistent with the source data source and is 0 seconds. You can click on to view the synchronization delay on the page.
- If the precheck fails, click on on the right side of the target check item to investigate the cause of the failure, manually fix it, and then click to re-execute the precheck until it passes.
- Items in with can be repaired or ignored depending on the specific situation.
On the page, when prompted with , the sync task begins to run. At this point, you can perform the following operations:
- Click on to view the execution status of each stage of the sync task.
- Click on to return to the task list page.

View Synchronization Results

Log in to the NineData Console.
Click on > in the left navigation bar.

On the page, click on the of the target synchronization task, and the page is explained as follows.

oracle_result

Number	Function	Description
1	Synchronization 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 this 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. For more information, see Introduction to Operational Monitoring.
3	More	Pause: Pause the task. Only tasks with the status Running can be selected. Terminate: End tasks that are incomplete or in progress (i.e., in incremental synchronization). After terminating the task, it cannot be restarted, so operate with caution. If the synchronized objects include triggers, the trigger replication options will pop up, so choose as needed. Delete: Delete the task. Once the task is deleted, it cannot be recovered, so operate with caution.
4	Structure Replication (Displayed in scenarios including structure replication)	Show the progress and details of structure replication. Click on the Logs 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 Operation column on the right of the target object in the list: You can view SQL playback.
5	Full Replication (Displayed in scenarios including full replication)	Show the progress and details of full replication. Click on Monitoring on the right side of the page: View various monitoring indicators during full replication. During full replication, you can also click Rate Limit Settings on the right side of the monitoring indicators page to limit the rate of writing to the target data source per second. Click on Logs 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 including incremental replication)	Display various monitoring indicators of incremental replication. Click on on the right side of the page: View the operations currently being performed by the current replication task, including: : The replication task is performed in multiple threads, showing the current thread number in progress. : Details of the SQL statement currently being executed by the current thread. : The response time of the current thread. If this value increases, it may indicate that the current thread is stuck for some reason. : The timestamp when the current thread is opened. : The status of the current thread. Click on Rate Limit Settings on the right side: Limit the rate of writing to the target data source per second. The unit is rows/second. Click on Logs 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	Show the modification records of synchronized objects. Click on Modify Synchronized Objects on the right side of the page to configure synchronized objects. Click on on the right side of the page: View the latest information.
8	Data Comparison	Show the results of data comparison between the source data source and the target data source. If you have not enabled data comparison, click Enable Data Comparison in the page. Click on Recompare on the right side of the page: Reinitiate the comparison of data between the current source and target. Click on the date to view the list of all comparison results, and click on the target list item to switch to the details of this comparison result. Click on Logs on the right side of the page: View the execution logs of consistency comparison. Click on Monitoring on the right side of the page: View the trend chart of comparison RPS (records per second). Click Details to view records from earlier. Click on in the Operation column on the right of the comparison list (displayed in case of inconsistency): View the comparison details between the source and target. Click on in the Operation column on the right of the comparison list (displayed in case of inconsistency): Generate change SQL, which you can copy directly to the target data source to execute and modify inconsistent content.
9	Expand	Show detailed information of the current replication task, including Replication Type, Replication Objects, Start Time, etc.

Appendix 1: Data Type Mapping Table

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

Type	Oracle Data Type	MySQL Data Type
Build-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)]	DATATIME
	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
Oralce supplied Data Type	AnyData	TEXT

### Appendix 2: Pre-Check Item Checklist

Check Item	Check Content
Source Data Source Connection Check	Check the status of the source data source gateway, instance accessibility, and accuracy of username and password
Target Data Source Connection Check	Check the status of the target data source gateway, instance accessibility, and accuracy of username and password
Target Database Permission Check	Check if the account permissions in the target database meet the requirements
Source Database Permission Check	Check if the account permissions in the source database meet the requirements
Target Data Source Trigger Check	Check if triggers exist in the target database
Target Database Data Existence Check	Check if data exists for the objects to be replicated in the target database
Target Database Same Name Object Existence Check	Check if the objects to be replicated already exist in the target database
Source Database Log Archiving Mode Check	Check if the log archiving mode of the source database is ARCHIVELOG
Source Database Additional Logging Check	Source database additional logging must be enabled and set to ALL

Introduction to Data Replication

Oracle Replication to MySQL

Prerequisites​

Usage Restrictions​

Operation Steps​

View Synchronization Results​

Appendix 1: Data Type Mapping Table​

Related Documentation​

Prerequisites

Usage Restrictions

Operation Steps

View Synchronization Results

Appendix 1: Data Type Mapping Table

Related Documentation