Oracle to Oracle Data Replication

NineData Data Replication supports schema replication, full replication, and incremental replication between Oracle instances.

Overview

Oracle to Oracle replication is useful when you want to move data between Oracle instances while keeping the same database family and feature set.

Before you begin

• Add the source and target data sources to NineData. For instructions, see Add Data Source.

• Check the versions of the source and target data sources. The source version must be less than or equal to the target version.

  Source Data Source	Target Data Source
  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 editions 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	See Appendix 2: Oracle incremental replication account permission instructions in this document.	ALL Privileges ON database

• For incremental replication, make sure these settings are configured on the source data source:

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

    To check the current log mode, run:

    SELECT log_mode FROM v$database;

    If the log mode is NOARCHIVELOG, run the following 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

• Before you run a replication task, assess the performance of the source and target data sources. Run the task during off-peak hours when possible because full initialization consumes read and write resources.
• Each replicated table must have a primary key or unique constraint, and column names must be unique. Otherwise, duplicate rows may be replicated.

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.
   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. The switch on the right enables periodic full replication. For more information, see Periodic Full Replication. Incremental: After full synchronization completes, perform incremental synchronization based on the logs of the source data source.The icon is used to configure incremental operation types. Clear the operation types to exclude. 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. 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 (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 completes.
   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.

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: NineData 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.

   Other available 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.

Other available actions:

• Select 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.
• Select 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.
• Select 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 NineData 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 completes.
     • Schema+Full: Starts after full replication completes.
     • Full: Starts after full replication completes.
     • 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 if required.

8. On the Launch page, the Launch Successfully message appears, indicating that the synchronization task has started. 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 synchronization task. The task details page shows the following areas.

   

   Number	Function	Description
   1	Sync Delay	Shows the synchronization 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 migration.
   2	Configure Alerts	Configure alerts to receive failure notifications through the method you choose. For more information, see Introduction to operational monitoring.
   3	More	Pause: Pause a task whose status is Running. Terminate: Terminate a task that is unfinished or still being monitored, such as a task in incremental synchronization. A terminated task cannot be restarted. Proceed with caution. If the synchronized objects contain triggers, a trigger replication option appears. 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 schema replication progress and details. Click Logs to view schema replication logs. Click to view the latest information. Click View DDL in the Action column for a target object to view SQL playback.
   5	Full Replication (shown when full replication is included)	Shows full replication progress and details. Click Monitoring to view monitoring indicators during full replication. During full replication, click Flow Control Settings on the monitoring page to limit the write rate to the target data source. 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 task uses multiple threads for replication. This item shows the current thread number. Execute SQL: Details of the SQL statement that the current thread is executing. Response Time: The response time of the current thread. If this value increases, the thread may be blocked. Event Time: The timestamp when the current thread started. Status: The current thread status. Click Flow Control 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 modification records for synchronized objects. Click Modify Sync Object to configure the synchronization object . Click to view the latest information.
   8	Data Comparison	Shows the results of data comparison between the source and target data sources. This includes Structure Comparison and Data Comparison. 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 a date to view all comparison results, then click a result item to open its details. Click Logs to view consistency comparison logs. Click Monitoring (shown only for data comparison) to view the comparison RPS trend chart. Click Details to view earlier records. Click in the Action column of the comparison list to view source and target comparison details. Click when inconsistent data exists to generate change SQL. Copy the SQL to the target data source and run it to fix the inconsistency.
   9	Expand	Shows details of the current replication task, including Replication Type, Replication Object, Start Time, and more.

Appendix 1: Precheck items

Check item	What NineData checks
Target database same-name object existence check	Checks whether the objects to be replicated already exist in the target database.
Source data source connection check	Checks the source data source gateway status, instance accessibility, and username and password accuracy.
Target data source connection check	Checks the target data source 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 database data existence check	Checks whether data exists for the objects to be replicated in the target database.
Source database log archiving mode check	Checks whether the source database log archiving mode is ARCHIVELOG.
Source database additional logging check	Checks whether source database additional logging is enabled and set to ALL.

Appendix 2: Oracle incremental replication account permission instructions

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