Synchronize a self-managed Oracle database to Kafka - Data Transmission Service

Prerequisites

You have a source self-managed Oracle database and a destination Message Queue for Apache Kafka instance.

Note
For more information about the supported versions of the source database and the destination instance, see Overview of data synchronization scenarios.
ARCHIVELOG mode must be enabled, and the archive logs must have a reasonable retention period and be accessible. For more information, see ARCHIVELOG.
Supplemental logging, supplemental_log_data_pk, and supplemental_log_data_ui are enabled for the self-managed Oracle database. For more information, see Supplemental Logging.
The destination Message Queue for Apache Kafka instance must have more storage space than the data in the source self-managed Oracle database.
The destination Message Queue for Apache Kafka instance must have a topic to receive the synchronized data. For more information, see Step 1: Create a topic.
Before you start data synchronization, review the capabilities and limitations of Data Transmission Service (DTS) when the source database is Oracle and perform a database assessment with Advanced Database & Application Migration (ADAM) for a smooth cloud migration. For more information, see Limitations and preparations for Oracle databases and Database assessment overview.

Limitations

Note

DTS does not synchronize foreign keys from the source database to the destination database. Therefore, cascade operations and delete operations in the source database are not synchronized to the destination database.

Category	Description
Limits on the source database	Requirements for the objects to be synchronized: The tables to be synchronized must have PRIMARY KEY or UNIQUE constraints, and all fields must be unique. Otherwise, the destination database may contain duplicate data records. If the version of your Oracle database is 12c or later, the names of the tables to be synchronized cannot exceed 30 bytes in length. If you select tables as the objects to be synchronized and you want to edit the tables in the destination database, such as renaming tables or columns, you can synchronize up to 1,000 tables in a single data synchronization task. If you run a task to synchronize more than 1,000 tables, a request error occurs. In this case, we recommend that you split the tables and configure multiple tasks to synchronize the tables in batches or configure a task to synchronize the entire database. If the source database is an Oracle RAC database connected over Express Connect, you must specify a virtual IP address (VIP) for the database when you configure the data synchronization task. If the self-managed Oracle database is an Oracle RAC database, you can only use a VIP rather than a Single Client Access Name (SCAN) IP address when you configure the data synchronization task. After you specify the VIP, node failover of the Oracle RAC database is not supported. The redo logging and archive logging features must be enabled. Note If you perform only incremental data synchronization, the redo logs and archive logs of the source database must be stored for more than 24 hours. If you perform both full data synchronization and incremental data synchronization, the redo logs and archive logs of the source database must be stored for at least seven days. Otherwise, DTS may fail to obtain the redo logs and archive logs and the task may fail. In exceptional circumstances, data inconsistency or loss may occur. After the full data synchronization is complete, you can set the retention period to more than 24 hours. Make sure that you set the retention period of redo logs and archive logs in accordance with the preceding requirements. Otherwise, the service reliability and performance stated in the Service Level Agreement (SLA) of DTS may not be guaranteed. If you perform a primary/secondary switchover on the source database when the data synchronization task is running, the task fails. If the data to be synchronized contains an empty string of the VARCHAR2 type (Oracle processes it as null) and the corresponding column in the destination database has a NOT NULL constraint, the data synchronization task fails. If the table to be synchronized has the Fine-Grained Audit (FGA) policy enabled, DTS cannot detect the `ORA_ROWSCN` pseudocolumn, which causes the synchronization task to fail. Note You can disable the FGA policy for the table to be synchronized, or exclude the table from synchronization. During data synchronization, do not update LONGTEXT fields. Otherwise, the data synchronization task fails. Do not run DDL operations that change database or table schemas during schema synchronization or full synchronization. Otherwise, the synchronization task fails. Note During full synchronization, DTS queries the source database. This creates metadata locks that may block DDL operations on the source database.
Other limits	DTS does not synchronize the data in a renamed table to the destination Kafka cluster. This applies if the new table name is not included in the objects to be synchronized. To synchronize the data in a renamed table to the destination Kafka cluster, you must perform Modify Synchronized Objects operation. For more information, see Add synchronization objects. External tables cannot be synchronized. Indexes, partitions, views, procedures, functions, triggers, foreign keys, table comments, and column comments cannot be synchronized. During incremental data synchronization, you cannot use Oracle Data Pump to write data to the source database. Otherwise, data loss may occur. Before you synchronize data, evaluate the impact of data synchronization on the performance of the source and destination databases. We recommend that you synchronize data during off-peak hours. During initial full data synchronization, DTS uses the read and write resources of the source and destination databases. This may increase the loads on the database servers. During full data synchronization, concurrent INSERT operations cause fragmentation in the tables of the destination database. After the full data synchronization is complete, the size of the used tablespace of the destination database is larger than that of the source database. DTS calculates synchronization latency based on the timestamp of the latest synchronized data in the destination database and the current timestamp in the source database. If no DML operation is performed on the source database for a long time, the synchronization latency may be inaccurate. If the latency of the synchronization task is excessively high, you can perform a DML operation on the source database to update the latency. Note If you select an entire database as the object to synchronize, you can create a heartbeat table. The heartbeat table is updated or receives data every second. During data synchronization, we recommend that you use only DTS to write data to the destination database. This prevents data inconsistency between the source and destination databases. For example, if you use tools other than DTS to write data to the destination database, data loss may occur in the destination database when you use DMS to perform online DDL operations. During data synchronization, if the destination Kafka cluster is scaled up or down, you need to restart the instance. If a task fails, DTS support staff will attempt to restore it within eight hours. During restoration, they may restart the task or adjust its parameters. Note Only DTS task parameters are modified—not database parameters. Parameters that may be adjusted include those listed in Modify instance parameters.

Billing

Synchronization type	Pricing
Schema synchronization and full data synchronization	Free of charge.
Incremental data synchronization	Charged. For more information, see Billing overview.

Single record size limit

The maximum size of a single record that can be written to Kafka is 10 MB. If a source row exceeds this limit, DTS interrupts the task because it cannot write the oversized record. In this scenario, we recommend that you do not synchronize the table. If you must synchronize the table, configure the DTS task to include only a subset of its columns, excluding those with large fields. For a running task, first remove the table from the list of synchronized objects. Then, add the table again, but this time, exclude the columns that contain large fields.

Synchronization topologies

One-way one-to-one synchronization
One-way one-to-many synchronization
One-way many-to-one synchronization
One-way cascade synchronization

For more information about these synchronization topologies and important notes, see data synchronization topologies.

Supported SQL operations

Operation type	SQL statement
DML	INSERT, UPDATE, and DELETE
DDL	CREATE TABLE, ALTER TABLE, DROP TABLE, RENAME TABLE, and TRUNCATE TABLE CREATE VIEW, ALTER VIEW, and DROP VIEW CREATE PROCEDURE, ALTER PROCEDURE, and DROP PROCEDURE CREATE FUNCTION, DROP FUNCTION, CREATE TRIGGER, and DROP TRIGGER CREATE INDEX and DROP INDEX

Database account permissions

Database	Required permissions	Account setup
Self-managed Oracle database	Requires fine-grained permissions.	Prepare a database account, CREATE USER, and GRANT.

Important

You must also enable archive logs and supplemental logs to capture incremental data changes. For more information, see Database configuration.

Procedure

Go to the data synchronization task list page in the destination region. You can do this in one of two ways.
DTS console
1. Log on to the DTS console.
2. In the navigation pane on the left, click Data Synchronization.
3. In the upper-left corner of the page, select the region where the synchronization instance is located.
DMS console
Note
The actual steps may vary depending on the mode and layout of the DMS console. For more information, see Simple mode console and Customize the layout and style of the DMS console.
1. Log on to the DMS console.
2. In the top menu bar, choose Data + AI > DTS (DTS) > Data Synchronization.
3. To the right of Data Synchronization Tasks, select the region of the synchronization instance.
Click Create Task to navigate to the task configuration page.

Configure the source and destination databases.

Category	Parameter	Description
N/A	Task Name	DTS automatically generates a task name. We recommend that you specify a descriptive name for easy identification. The name does not need to be unique.
Source Database	Database Type	Select Oracle.
	Connection Type	Select an access method based on where your source database is deployed. This example uses Self-managed Database on ECS. Note If the source instance is a self-managed database, you must complete the required preparations. For more information, see Preparation overview.
	Instance Region	Select the region where the self-managed Oracle database is located.
	ECS Instance ID	Select the ID of the ECS instance that hosts the self-managed Oracle database.
	Port number	Enter the service port of the self-managed Oracle database. The default value is 1521.
	Oracle Type	Non-RAC Instance: If you select this option, you must also enter the SID. RAC or PDB Instance: If you select this option, you must also enter the Service Name. Important Although the option is labeled "RAC or PDB Instance", RAC instances are not supported. This example uses Non-RAC Instance.
	Database Account	Enter the database account for the self-managed Oracle database. For information about the required permissions, see Permissions required for database accounts.
	Database Password	Enter the password for the specified database account.
Destination Database	Database Type	Select Kafka.
	Connection Type	Select Express Connect, VPN Gateway, or Smart Access Gateway. Note In this scenario, the Message Queue for Apache Kafka instance serves as a self-managed Kafka database for the synchronization instance.
	Instance Region	Select the region where the destination Message Queue for Apache Kafka instance is located.
	Connected VPC	Select the VPC ID of the destination Message Queue for Apache Kafka instance. You can find the VPC ID on the Basic Information page of the Kafka instance.
	Hostname or IP address	Enter an IP address from the Default Endpoint of the Message Queue for Apache Kafka instance. Note You can find the IP address for the Default Endpoint on the Basic Information page of the Message Queue for Apache Kafka instance.
	Port Number	Enter the service port of the Message Queue for Apache Kafka instance. The default value is 9092.
	Database Account	Enter the database account of the Message Queue for Apache Kafka instance. Note If the Message Queue for Apache Kafka instance is a VPC-connected instance, you do not need to configure Database Account and Database Password.
	Database Password	Enter the password for the specified database account.
	Kafka Version	Select the version that matches your Kafka instance.
	Connection method	Select Non-encrypted or SCRAM-SHA-256 based on your business and security requirements.
	Topic	Select the topic to receive data.
	Use Kafka Schema Registry	Kafka Schema Registry is a metadata-serving layer. It provides a RESTful API for storing and retrieving Avro schemas. No: Do not use Kafka Schema Registry. Yes: Use Kafka Schema Registry. You must specify the URL or IP address that is registered in Kafka Schema Registry for your Avro schemas.

After the configuration is complete, click Test Connectivity and Proceed at the bottom of the page. In the CIDR Blocks of DTS Servers dialog box, click Test Connectivity.
Note
Ensure that the IP address blocks of the DTS service are added to the security settings of the source and destination databases, either automatically or manually, to allow access from DTS servers. For more information, see Add the IP address whitelist of DTS servers.

Configure the task objects.

On the Configure Objects page, specify the objects to synchronize.

Parameter	Description
Synchronization Type	DTS always selects Incremental Data Synchronization. By default, you must also select Schema Synchronization and Full Data Synchronization. After the precheck, DTS initializes the destination cluster with the full data of the selected source objects, which serves as the baseline for subsequent incremental synchronization.
Processing Mode for Existing Destination Tables	Precheck and Report Errors: Checks for tables with the same names in the destination database. If any tables with the same names are found, an error is reported during the precheck and the data synchronization task does not start. Otherwise, the precheck is successful. Note If you cannot delete or rename the table with the same name in the destination database, you can map it to a different name in the destination. For more information, see Database Table Column Name Mapping. Ignore Errors and Proceed: Skips the check for tables with the same name in the destination database. Warning Selecting Ignore Errors and Proceed may cause data inconsistency and put your business at risk. For example: If the table schemas are consistent and a record in the destination database has the same primary key or unique key value as a record in the source database: During full data synchronization, DTS retains the destination record and skips the source record. During incremental synchronization, DTS overwrites the destination record with the source record. If the table schemas are inconsistent, data initialization may fail. This can result in only partial data synchronization or a complete synchronization failure. Use with caution.
Data Format in Kafka	Select the data format in which DTS writes data to the Kafka instance. If you select DTS Avro, you must parse the data based on the DTS Avro schema definition. For more information, see DTS Avro Schema Definition and DTS Avro Deserialization Example. If you select Shareplex Json, see Shareplex Json for parameter descriptions and examples.
Kafka Data Compression Format	Select a compression format for Kafka messages based on your business requirements. LZ4 (Default): offers a low compression ratio and high compression speed. GZIP: offers a high compression ratio and low compression speed. Note GZIP compression consumes significant CPU resources. Snappy: offers a medium compression ratio and medium compression speed.
Policy for Shipping Data to Kafka Partitions	Select a policy that meets your business requirements.
Message acknowledgement mechanism	Select an acknowledgment mechanism that meets your business requirements.
Topic That Stores DDL Information	Select a topic to store DDL information. If you do not select one, DDL information is stored in the data-receiving topic by default.
Capitalization of Object Names in Destination Instance	Configure the case-sensitivity policy for database, table, and column names in the destination instance. By default, the DTS default policy is selected. You can also choose to use the default policy of the source or destination database. For more information, see Case policy for destination object names.
Source Objects	In the Source Objects box, click the objects, and then click to move them to the Selected Objects box. Note You can select objects at the database, table, or column level. If you select only tables or columns, DTS does not synchronize other object types (such as views, triggers, and stored procedures).
Selected Objects	No additional configuration is required in this example. You can use the mapping feature to set the topic name, number of partitions, and partition key for the source tables in the destination Kafka instance. For more information, see Mapping information. Note If you use object name mapping, synchronization may fail for other objects that depend on the mapped object. To select the SQL operations for incremental synchronization, right-click an object in the Selected Objects section and select the SQL operations to synchronize in the dialog box that appears.

Click Next: Advanced Settings.

Parameter	Description
Dedicated Cluster for Task Scheduling	By default, DTS uses a shared cluster for tasks, so you do not need to make a selection. For greater task stability, you can purchase a dedicated cluster to run the DTS synchronization task. For more information, see What is a DTS dedicated cluster?.
Retry Time for Failed Connections	If the connection to the source or destination database fails after the synchronization task starts, DTS reports an error and immediately begins to retry the connection. The default retry duration is 720 minutes. You can customize the retry time to a value from 10 to 1,440 minutes. We recommend a duration of 30 minutes or more. If the connection is restored within this period, the task resumes automatically. Otherwise, the task fails. Note If multiple DTS instances (e.g., Instance A and B) share a source or destination, DTS uses the shortest configured retry duration (e.g., 30 minutes for A, 60 for B, so 30 minutes is used) for all instances. DTS charges for task runtime during connection retries. Set a custom duration based on your business needs, or release the DTS instance promptly after you release the source/destination instances.
Retry Time for Other Issues	If a non-connection issue (e.g., a DDL or DML execution error) occurs, DTS reports an error and immediately retries the operation. The default retry duration is 10 minutes. You can also customize the retry time to a value from 1 to 1,440 minutes. We recommend a duration of 10 minutes or more. If the related operations succeed within the set retry time, the synchronization task automatically resumes. Otherwise, the task fails. Important The value of Retry Time for Other Issues must be less than that of Retry Time for Failed Connections.
Enable Throttling for Full Data Synchronization	During full data synchronization, DTS consumes read and write resources from the source and destination databases, which can increase their load. To mitigate pressure on the destination database, you can limit the migration rate by setting Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s). Note This parameter is available only if Synchronization Types is set to Full Data Synchronization. You can also adjust the rate of full data synchronization when the synchronization instance is running.
Enable Throttling for Incremental Data Synchronization	You can also limit the incremental synchronization rate to reduce pressure on the destination database by setting RPS of Incremental Data Synchronization and Data synchronization speed for incremental synchronization (MB/s).
Environment Tag	You can select an environment tag to identify the instance based on your needs. No configuration is required in this example.
Actual Write Code	You can select the character encoding for the data written to the destination database based on your needs.
Configure ETL	Choose whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values: Yes: Enables the ETL feature. Enter data processing statements in the code editor. For more information, see Configure ETL in a data migration or data synchronization task. No: Disables the ETL feature.
Monitoring and Alerting	Choose whether to set up alerts. If the synchronization fails or the latency exceeds the specified threshold, DTS sends a notification to the alert contacts. No: No alerts are configured. Yes: Configures alerts. You must also set the alert threshold and alert notifications. For more information, see Configure monitoring and alerting during task configuration.

Save the task and perform a precheck.
- To view the parameters for configuring this instance via an API operation, hover over the Next: Save Task Settings and Precheck button and click Preview OpenAPI parameters in the tooltip.
- If you have finished viewing the API parameters, click Next: Save Task Settings and Precheck at the bottom of the page.
Note
- Before a synchronization task starts, DTS performs a precheck. You can start the task only if the precheck passes.
- If the precheck fails, click View Details next to the failed item, fix the issue as prompted, and then rerun the precheck.
- If the precheck generates warnings:
  For non-ignorable warning, click View Details next to the item, fix the issue as prompted, and run the precheck again.
  For ignorable warnings, you can bypass them by clicking Confirm Alert Details, then Ignore, and then OK. Finally, click Precheck Again to skip the warning and run the precheck again. Ignoring precheck warnings may lead to data inconsistencies and other business risks. Proceed with caution.

Purchase the instance.

When the Success Rate reaches 100%, click Next: Purchase Instance.

On the Purchase page, select the billing method and link specifications for the data synchronization instance. For more information, see the following table.

Category	Parameter	Description
New Instance Class	Billing Method	Subscription: You pay upfront for a specific duration. This is cost-effective for long-term, continuous tasks. Pay-as-you-go: You are billed hourly for actual usage. This is ideal for short-term or test tasks, as you can release the instance at any time to save costs.
	Resource Group Settings	The resource group to which the instance belongs. The default is default resource group. For more information, see What is Resource Management?.
	Instance Class	DTS offers synchronization specifications at different performance levels that affect the synchronization rate. Select a specification based on your business requirements. For more information, see Data synchronization link specifications.
	Subscription Duration	In subscription mode, select the duration and quantity of the instance. Monthly options range from 1 to 9 months. Yearly options include 1, 2, 3, or 5 years. Note This option appears only when the billing method is Subscription.

Read and select the checkbox for Data Transmission Service (Pay-as-you-go) Service Terms.
Click Buy and Start, and then click OK in the OK dialog box.
You can monitor the task progress on the data synchronization page.

Mappings

In the Selected Objects area, hover over the destination topic name.
Click the Edit button that appears next to the destination topic name.

In the Edit Table dialog box, configure the mapping settings.