Data Replication Between Oracle Instances

NineData data replication supports data synchronization between Oracle to Oracle data sources.

Prerequisites

Ensure that both the source and target data sources have been added to NineData. For instructions on adding data sources, please refer to Add Data Source.

Check the version numbers of the source and target data sources. Note that the version number of the source data source must be less than or equal to the target data source.

Source Datasource	Target Datasource
Oracle 23ai	Oracle 23ai
Oracle 21c	Oracle 23ai、21c
Oracle 19c	Oracle 23ai、21c、19c
Oracle 18c	Oracle 23ai、21c、19c、18c
Oracle 12c	Oracle 23ai、21c、19c、18c、12c
Oracle 11g	Oracle 23ai、21c、19c、18c、12c、11g

Supported Oracle versions (product lines) include:
- Oracle Enterprise Edition
- Oracle Standard Edition
- Oracle Express Edition
- Oracle Personal Edition

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 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	Please refer to Appendix 2: Oracle incremental replication account permission instructions in this document.	ALL Privileges ON database

For incremental replication, ensure the following configurations are made in the source data source:

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

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 command to enable archiving: ALTER DATABASE ARCHIVELOG;
4. Open the database: ALTER DATABASE OPEN;

Supplemental Log is enabled (not enabled by default).

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 logging at the database level for all tables and columns, consuming more resources.
- ALTER TABLE <database_name>.<table_name> ADD SUPPLEMENTAL LOG DATA (ALL) COLUMNS;
- ALTER DATABASE ADD SUPPLEMENTAL LOG DATA;
// Enables supplemental logging on a specific table, affecting all columns in that table.

Usage Restrictions

Evaluate the performance of both source and target data sources before executing data synchronization. It is recommended to perform data synchronization during low business hours. Otherwise, full data initialization will consume certain read-write resources from both 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. Otherwise, duplicate synchronization of the same data may occur.

Operating 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.

Log in to the NineData Console.
In the left navigation pane, click Replication > Data Replication.
On the Replication page, click Create Replication in the upper-right corner.

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.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.
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.
Trigger	Choose whether to activate triggers in the target database during data replication. This option is disabled by default. Click the switch to enable it. Note: If the target contains foreign key constraints, enabling triggers may cause the replication task to fail. Use this option with caution.

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.

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.

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.
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.

View Sync Results

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

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

oracle_result

Number	Function	Description
1	Sync Delay	The data synchronization delay between the source and target data sources. A delay of 0 seconds indicates no delay between the two ends, and 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, please refer to Introduction to Operations Monitoring.
3	More	Pause: Pause the task. Only tasks with the status Running can be paused. Terminate: End unfinished or listening (i.e., incremental sync) tasks. After terminating the task, it cannot be restarted, so please operate with caution. If the synchronized objects contain triggers, the trigger replication options will pop up, please choose as needed. Delete: Delete the task. Once the task is deleted, it cannot be recovered, so please operate with caution.
4	Structure Replication (displayed in scenarios involving structure replication)	Display the progress and details of structure replication. Click on 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 Action column on the right side of the target object in the list: View SQL replay.
5	Full Replication (displayed in scenarios involving full replication)	Display 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 the full replication process, 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. 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 involving incremental replication)	Display 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: The replication task is performed by multiple threads to execute replication operations, showing 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 means that the current thread may be stuck for some reason. Event Time: The timestamp when the current thread was started. Status: The current status of the 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 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	Display modification records of synchronized objects. Click on Modify Sync Object on the right side of the page to configure the synchronization object . Click on on the right side of the page: View the latest information.
8	Data Comparison	Display the results of data comparison between the source and target data sources. Includes Structure Comparison and Data Comparison. If you have not enabled data comparison, click on Enable Data Comparison on the page. Click on Recompare on the right side of the page: Reinitiate the comparison of current data on both the source and target ends. 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 (only displayed in data comparison): View the trend chart of RPS (records per second compared) during the comparison. Click Details to view earlier records. Click in the Action column on the right side of the comparison list: View the comparison details of the source and target ends. Click (displayed in 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, including Replication Type, Replication Object, Start Time, etc.

Appendix: Pre-Check Item Checklist

Check Item	Check Content
Target Database Same Name Object Existence Check	Check if the objects to be replicated already exist in the target database
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 Database Data Existence Check	Check if data exists for the objects to be replicated 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

Appendix 2: Oracle incremental replication account permission instructions

Below Oracle 12c
Oracle 12c and above

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;

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;

Introduction to Data Replication

Data Replication Between Oracle Instances

Prerequisites​

Usage Restrictions​

Operating Steps​

View Sync Results​

Appendix: Pre-Check Item Checklist​

Appendix 2: Oracle incremental replication account permission instructions​

Related Documentation​