From Oracle to Kafka

Supported Source and Destination Databases

Suggestions

• The success of database synchronization depends on environment and manual operations. To ensure a smooth synchronization, perform a synchronization trial before you start the synchronization to help you detect and resolve problems in advance.
• It is recommended that you start a task during off-peak hours to minimize the impact of synchronization on your services.
• For more information about the impact of DRS on databases, see How Does DRS Affect the Source and Destination Databases?

Precautions

Before creating a synchronization task, read the following notes:

• You are advised to create an independent database account for DRS task connection to prevent task failures caused by database account password modification.
• After changing the account passwords for the source and destination databases, modify the connection information of the DRS task by referring to Modifying Connection Information to prevent automatic retry after a task failure. Automatic retry will lock the database accounts.

Procedure

1. On the Data Synchronization Management page, click Create Synchronization Task.
2. On the Create Synchronization Instance page, select a region and project, specify the task name, description, and the synchronization instance details, and click Create Now.
   • Task information description
     Figure 1 Synchronization task information
     

     Table 3 Task information

     Parameter	Description
     Region	The region where the replication instance is deployed. You can change the region.
     Project	The project corresponds to the current region and can be changed.
     Task Name	The task name must start with a letter and consist of 4 to 50 characters. It can contain only letters, digits, hyphens (-), and underscores (_).
     Description	The description consists of a maximum of 256 characters and cannot contain special characters !=<>'&"\

   • Synchronization instance details
     Figure 2 Synchronization instance details
     

     Table 4 Synchronization instance settings

     Parameter	Description
     Data Flow	Choose Self-built to self-built.
     Source DB Engine	Select Oracle.
     Destination DB Engine	Select Kafka.
     Network Type	The Public network is used as an example. Available options: VPC, Public network and VPN or Direct Connect
     DRS Task Type	Type of the DRS task. The value can be Single-AZ or Dual-AZ. Dual-AZ: This architecture provides HA, improving the reliability of DRS tasks. After a dual-AZ task is created, DRS creates two subtasks, each running in the primary and standby AZs. If the subtask in the primary AZ fails, DRS automatically starts the subtask in the standby AZ to continue the synchronization. This deployment is for scenarios where there is a lot of service data, long-term synchronization is required, and there are strict limits on how much service downtime can be tolerated. Single-AZ: Single-node deployment is used. The synchronization task will be created on only one node to save money. This deployment is for scenarios where there is a small amount of service data, short-term synchronization is required, and there is no requirement on service downtime. This option is available only in specific scenarios. For details, see Performing a Switchover for a Dual-AZ Task.
     VPC	Select an available VPC.
     Synchronization Instance Subnet	Select the subnet where the synchronization instance is located. You can also click View Subnets to go to the network console to view the subnet where the instance resides. By default, the DRS instance and the destination DB instance are in the same subnet. You need to select the subnet where the DRS instance resides, and there are available IP addresses for the subnet. To ensure that the synchronization instance is successfully created, only subnets with DHCP enabled are displayed.
     Security Group	Select a security group. You can use security group rules to allow or deny access to the instance.
     Synchronization Mode	Incremental Through log parsing, incremental data generated on the source database is synchronized to the destination database. During synchronization, the source database continues to provide services for external systems with zero downtime.
     Specify EIP	This parameter is available when you select Public network for Network Type. Select an EIP to be bound to the DRS instance. DRS will automatically bind the specified EIP to the DRS instance and unbind the EIP after the task is complete. The number of specified EIPs must be the consistent with that of DB instances. If DRS Task Type is set to Dual-AZ, you need to specify the primary and standby IP addresses. For details about the data transfer fee generated using a public network, see EIP Price Calculator.

   • Task Type
     Figure 3 Task type
     

     Table 5 Task type information

     Parameter	Description
     Specifications	DRS instance specifications. Different specifications have different performance upper limits. For details, see Real-Time Synchronization. NOTE: DRS allows you to upgrade specifications only for single-AZ synchronization tasks. Task specifications cannot be downgraded. For details, see Changing Specifications.
     AZ	Select the AZ where you want to create the DRS task. Selecting the one housing the source or destination database can provide better performance. If DRS Task Type is set to Dual-AZ, you can specify Primary AZ and Standby AZ. Figure 4 AZ

   • Enterprise Project and Tags
     Figure 5 Enterprise Project and Tags
     

     Table 6 Enterprise Project and Tags

     Parameter	Description
     Enterprise Project	An enterprise project you would like to use to centrally manage your cloud resources and members. Select an enterprise project from the drop-down list. The default project is default. For more information about enterprise project, see Enterprise Management User Guide. To customize an enterprise project, click Enterprise in the upper right corner of the console. The Enterprise Project Management Service page is displayed. For details, see Creating an Enterprise Project in Enterprise Management User Guide.
     Tags	Tags a task. This configuration is optional. Adding tags helps you better identify and manage your tasks. Each task can have up to 20 tags. If your organization has configured tag policies for DRS, add tags to tasks based on the policies. If a tag does not comply with the policies, task creation may fail. Contact your organization administrator to learn more about tag policies. After a task is created, you can view its tag details on the Tags tab. For details, see Tag Management.

   

   If a task fails to be created, DRS retains the task for three days by default. After three days, the task automatically stops.

3. On the Configure Source and Destination Databases page, wait until the synchronization instance is created. Then, specify source and destination database information and click Test Connection for both the source and destination databases to check whether they have been connected to the synchronization instance. After the connection tests are successful, select the check box before the agreement and click Next.
   Figure 6 Source database information
   

   Table 7 Source database settings

   Parameter	Description
   IP Address or Domain Name	The IP address or domain name of the source database. NOTE: For a RAC cluster, use a scan IP address to improve access performance.
   Port	The port of the source database. Range: 1 – 65535
   Database Service Name	Enter a database service name (Service Name/SID). The client can connect to the Oracle database through the database service name. For details about how to query the database service name, see the prompt on the GUI.
   PDB Name	Container database (CDB) and pluggable database (PDB) are new features in Oracle 12c and later versions. This function is optional, but it must be enabled if you want to migrate only PDB tables. Enter the service name, SID, username, and password of the CDB that contains the PDB tables to be migrated.
   Database Username	The username for accessing the source database.
   Database Password	The password for the database username.
   SSL Connection	SSL encrypts the connections between the source and destination databases. If SSL is enabled, upload the SSL CA root certificate. NOTE: The maximum size of a single certificate file that can be uploaded is 500 KB. If SSL is disabled, your data may be at risk.

   

   The IP address, domain name, username, and password of the source database are encrypted and stored in DRS, and will be cleared after the task is deleted.

   Figure 7 Destination database information
   

   Table 8 Destination database settings

   Parameter	Description
   IP Address or Domain Name	The IP address or domain name of the destination database.
   Security Protocol	Available options: PLAINTEXT, SSL, SASL_PLAINTEXT, and SASL_SSL. For details, see Kafka Authentication.

4. On the Set Synchronization Task page, select a topic and objects to be synchronized, and then click Next.
   Figure 8 Synchronization mode
   

   Table 9 Synchronization mode and object

   Parameter	Description
   Synchronize DML	Select the DML operations to be synchronized. By default, all DML operations are selected. If you do not select Delete, DELETE statements in the incremental data of the source database will not be synchronized, which may cause a data inconsistency. As a result, there may be a data conflict or the task may fail.
   Synchronize DDLs	Controls whether to synchronize DDLs to Kafka. If Synchronize DDLs is enabled and Partitions are identified by the hash values of the primary key is selected, DDLs are hashed based on the table name because the DDLs do not have the primary key value. In other cases, the synchronization policy is the same as the partition policy.
   All Data	Controls whether to synchronize all data in a single row. DRS parses the source database logs to synchronize incremental data. The data integrity in a single row depends on whether the values of all columns are recorded in the logs. If all data is required for the synchronization object, all-level supplemental logging must be enabled in the source database to record all column values of a single row data. This option is associated with the verification of the supplemental logging level in the source database in the pre-check phase. DRS incremental synchronization has the minimum requirement of table-level PK/UI supplemental logging. For details, see How Do I Check Supplemental Logging of the Source Oracle Database?
   Topic Synchronization Policy	Topic synchronization policy. The options are as follows: Select A specified topic if the data volume of the source database is small. Select Automatically generated based on the schema name if each schema contains a lot of data. Select Automatically generated using the schema_name-table_name format if each table contains a lot of data.
   Topic	Select the topic to be synchronized to the destination database. This parameter is available when Topic Synchronization Policy is set to A specified topic.
   Topic Name Format	Topic name format. This parameter is available when Topic Synchronization Policy is set to Auto-generated topics. Due to Kafka restrictions, a topic name can contain only ASCII characters, periods (.), underscores (_), and hyphens (-). If a topic name exceeds the limit, the topic fails to be created and the task is abnormal. If a topic name contains a database object name, ensure that the characters in the object name meet the Kafka topic naming requirements. The topic name format supports the schema and tablename variables. Other characters are used as constants. Replace $schema$ with the schema name and $tablename$ with the table name. For example, if this parameter is set to $schema$-$tablename$, the schema name is schema1, and the table name is tab1 when Oracle is the source, the topic name is schema1-tab1.
   Number of Partitions	This parameter is available when Topic Synchronization Policy is set to Auto-generated topics. The number of partitions of a topic. Each topic can have multiple partitions. More partitions can provide higher throughput but consume more resources. Set the number of partitions based on the actual situation of brokers.
   Replication Factor	This parameter is available when Topic Synchronization Policy is set to Auto-generated topics. Number of copies of a topic. Each topic can have multiple copies, and the copies are placed on different brokers in a cluster. The number of copies cannot exceed the number of brokers. Otherwise, the topic fails to be created.
   Synchronize Topic To	The policy for synchronizing topics to the Kafka partitions. If topics are synchronized to different partitions by the hash values of schema_name.table_name, the performance on a single table query can be improved. If topics are synchronized to different partitions by the hash values of the primary key, one table corresponds to one topic. This prevents data from being written to the same partition, and consumers can obtain data from different partitions concurrently. For a table without a primary key, if you select Partitions are identified by the hash values of the primary key, topics are synchronized to different partitions based on the hash values of schema_name.table_name. Partitions are differentiated by the hash values of schema_name: This mode applies to scenarios where one database corresponds to one topic, preventing data in multiple schemas from being written to the same partition, so that consumers can obtain data from different partitions concurrently. If topics are synchronized to partition 0, data is sent using multiple threads by default. This ensures strong consistency but write performance is impacted. If strong transaction consistency is required, you are advised to select this option and contact O&M personnel to change to single-thread Kafka write, or set the topic synchronization policy to Automatically generated based on the table name.
   Data Format in Kafka	Select the format of data sent from the Oracle database to the Kafka. Avro refers to binary encoded format. Json refers to data interchange format. For details, see Kafka Message Format.
   Synchronization Object	The left pane displays the source database objects, and the right pane displays the selected objects. You can select Tables or Import object file for Synchronization Object as required. If you select Import object file for Synchronization Object, different tables can be synchronized to different topics at the destination end. For details about the import procedure and description, Importing Synchronization Objects. When you select Import object file, you can use the mapping function in Changing Object Names (Mapping Object Names) only when the topic synchronization policy is set to A specific topic. Otherwise, topics are generated based on the name format. NOTE: To quickly select the desired database objects, you can use the search function. If there are changes made to the source databases or objects, click in the upper right corner to update the objects to be synchronized. If an object name contains spaces, the spaces before and after the object name are not displayed. If there are two or more consecutive spaces in the middle of the object name, only one space is displayed. The name of the selected synchronization object cannot contain spaces.

5. On the Check Task page, check the synchronization task.
   • If any check fails, review the cause and rectify the fault. After the fault is rectified, click Check Again.

     For details about how to handle check failures, see Solutions to Failed Check Items in Data Replication Service User Guide.

   • If all check items are successful, click Next.
     

     You can proceed to the next step only when all checks are successful. If there are any items that require confirmation, view and confirm the details first before proceeding to the next step.

6. On the displayed page, specify Start Time, Send Notifications, SMN Topic, Delay Threshold (s), and Stop Abnormal Tasks After, confirm that the configured information is correct, select the check box before the agreement, and click Submit to submit the task.
   Figure 9 Task startup settings
   

   Table 10 Task startup settings

   Parameter	Description
   Start Time	Set Start Time to Start upon task creation or Start at a specified time based on site requirements. NOTE: After a synchronization task is started, the performance of the source and destination databases may be affected. You are advised to start a synchronization task during off-peak hours.
   Send Notifications	This parameter is optional. After enabled, select a SMN topic. If the status, latency metric, or data of the migration task is abnormal, DRS will send you a notification.
   SMN Topic	This parameter is available only after you enable Send Notifications and create a topic on the SMN console and add a subscriber. For details, see Simple Message Notification User Guide.
   Delay Threshold (s)	During an incremental synchronization, a synchronization delay indicates a time difference (in seconds) of synchronization between the source and destination database. If the synchronization delay exceeds the threshold you specify, DRS will send alarms to the specified recipients. The value ranges from 0 to 3,600. To avoid repeated alarms caused by the fluctuation of delay, an alarm is sent only after the delay has exceeded the threshold for six minutes. NOTE: If the delay threshold is set to 0, no notifications will be sent to the recipient. In the early stages of an incremental synchronization, the synchronization delay is long because a large quantity of data is awaiting synchronization. In this case, no notifications will be sent. Before setting the delay threshold, enable Send Notifications.
   Data Exception Notification	This parameter is optional. After enabled, DRS will send a notification if the task data is abnormal.
   Stop Abnormal Tasks After	Number of days after which an abnormal task is automatically stopped. The value must range from 14 to 100. The default value is 14. NOTE: You can set this parameter only for pay-per-use tasks. Tasks in the abnormal state are still charged. If tasks remain in the abnormal state for a long time, they cannot be resumed. Abnormal tasks run longer than the period you set (unit: day) will automatically stop to avoid unnecessary fees.

7. After the task is submitted, you can view and manage it on the Data Synchronization Management page.
   • You can view the task status. For more information about task status, see Task Statuses.
   • You can click in the upper right corner to view the latest task status.
   • By default, DRS retains a task in the Configuration state for three days. After three days, DRS automatically deletes background resources, but the task status remains unchanged. When you configure the task again, DRS applies for resources for the task again. In this case, the IP address of the DRS instance changes.
   • For a public network task, DRS needs to delete background resources after you stop the task. The EIP bound to the task cannot be restored to the Unbound state until background resources are deleted.