Migrate data from a self-managed Oracle database to an ApsaraDB RDS for MySQL instance - Data Transmission Service

This topic describes how to migrate data from a self-managed Oracle database to an ApsaraDB RDS for MySQL instance by using Data Transmission Service (DTS). DTS supports schema migration, full data migration, and incremental data migration. When you migrate data from a self-managed Oracle database, you can select all of the supported migration types to ensure service continuity.

Prerequisites

The source self-managed Oracle database and the destination ApsaraDB RDS for MySQL instance are created.
Note
- For more information about how to create an ApsaraDB RDS for MySQL instance, see Create an ApsaraDB RDS for MySQL instance.
- For more information about the supported versions of the source database and the destination instance, see Overview of data migration scenarios.
The self-managed Oracle database is running in ARCHIVELOG mode. Archived log files are accessible and a suitable retention period is set for archived log files. For more information, see Managing Archived Redo Log Files.
The supplemental logging feature is enabled for the self-managed Oracle database, and the SUPPLEMENTAL_LOG_DATA_PK and SUPPLEMENTAL_LOG_DATA_UI parameters are set to Yes. For more information, see Supplemental Logging.
The destination ApsaraDB RDS for MySQL instance is created. For more information, see Create an ApsaraDB RDS for MySQL instance.

Limits

Note

During schema migration, DTS migrates foreign keys from the source database to the destination database.
During full data migration and incremental data migration, DTS temporarily disables the constraint check and cascade operations on foreign keys at the session level. If you perform the cascade and delete operations on the source database during data migration, data inconsistency may occur.

Category	Description
Limits on the source database	Bandwidth requirements: The server to which the source database belongs must have sufficient outbound bandwidth. Otherwise, the data migration speed decreases. If the source database is an Oracle RAC database connected over Express Connect, you must specify a VIP for the database when you configure the source database information. If the source database is an Oracle RAC database connected over Express Connect, VPN Gateway, Smart Access Gateway, Database Gateway, or Cloud Enterprise Network (CEN), you can use a single VIP rather than a Single Client Access Name (SCAN) IP address when you configure the source database information. After you specify the VIP, node failover is not supported for the Oracle RAC database. If a field in the source Oracle database contains an empty string of the VARCHAR2 type, which is evaluated as null in the Oracle database, and the corresponding field in the destination database has a NOT NULL constraint, the migration task fails. Requirements for the objects to migrate: The tables to be migrated 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 migrated cannot exceed 30 bytes in length. If you select tables as the objects to be migrated and you need to modify the tables in the destination database, such as renaming tables or columns, up to 1,000 tables can be migrated in a single data migration task. If you run a task to migrate more than 1,000 tables, a request error occurs. In this case, we recommend that you split the tables and configure multiple tasks to migrate the tables, or configure a task to migrate the entire database. If you want to migrate incremental data, you must make sure that the following requirements are met: The redo logging and archive logging must be enabled. If you perform only incremental data migration, the redo logs and archive logs of the source database must be stored for more than 24 hours. If you perform both full data migration and incremental data migration, the redo logs and archive logs of the source database must be stored for at least seven days. After full data migration is complete, you can set the retention period to more than 24 hours. Otherwise, DTS may fail to obtain the redo logs and archive logs and the task may fail. In extreme cases, data may be inconsistent or lost. Make sure that you set the retention period of redo logs and archive logs based on the preceding requirements. Otherwise, the service reliability and performance stated in the Service Level Agreement (SLA) of DTS may not be guaranteed. Limits on operations to be performed on the source database: During schema migration and full data migration, do not perform data definition language (DDL) operations to change the schemas of databases or tables. Otherwise, the data migration task fails. If you perform only full data migration, do not write data to the source database during data migration. Otherwise, data inconsistency between the source and destination databases may occur. To ensure data consistency, we recommend that you select Schema Migration, Full Data Migration, and Incremental Data Migration as the migration types. During data migration, do not update LONGTEXT fields. Otherwise, the data migration task fails.
Other limits	Before you migrate data, evaluate the impact of data migration on the performance of the source database and destination cluster. We recommend that you migrate data during off-peak hours. During full data migration, DTS uses the read and write resources of the source database and destination cluster. This may increase the loads on the database servers. During full data migration, concurrent INSERT operations cause fragmentation in the tables of the destination cluster. After full data migration is complete, the size of used tablespace of the destination cluster is larger than that of the source database. DTS attempts to resume data migration tasks that failed within the last seven days. Before you switch workloads to the destination cluster, you must stop or release the failed tasks. You can also execute the `REVOKE` statement to revoke the write permissions from the accounts that are used by DTS to access the destination database. Otherwise, the data in the source database overwrites the data in the destination database after the failed task is resumed.
Special cases	If the destination database runs on an ApsaraDB RDS for MySQL instance, take note of the following limits: Table names in the ApsaraDB RDS for MySQL instance are case-insensitive. If a table name in the source Oracle database contains uppercase letters, ApsaraDB RDS for MySQL converts all uppercase letters to lowercase letters before creating the table. If the source Oracle database contains identical table names that differ only in capitalization, these table names are identified as duplicate. During schema migration, the following message is returned: "The object already exists". To prevent name conflicts in the destination database, you can use the object name mapping feature to capitalize the table names when you configure the objects to be migrated. For more information, see Object name mapping. DTS automatically creates a destination database in the ApsaraDB RDS for MySQL instance. However, if the name of the source database is invalid, you must create a database in the ApsaraDB RDS for MySQL instance before you configure the data migration task. For more information, see Create a database for an ApsaraDB RDS for MySQL instance.

Billing

Migration type	Instance configuration fee	Internet traffic fee
Schema migration and full data migration	Free of charge.	Charged only when data is migrated from Alibaba Cloud over the Internet. For more information, see Billing overview.
Incremental data migration	Charged. For more information, see Billing overview.

Migration types

Migration type	Description
Schema migration	DTS migrates the schemas of objects to the destination database. DTS has the following limits on schema migration for tables and indexes: DTS does not support schema migration for nested tables. DTS converts clustered tables and index-organized tables (IOTs) into common tables in the destination database. DTS does not support schema migration for function-based indexes, domain indexes, bitmap indexes, or reverse indexes. Note DTS does not support schema migration for the following types of objects: view, synonym, stored procedure, function, package, and user-defined type. Warning In this topic, the source and destination databases are heterogeneous databases. The schemas of the source and destination databases may be inconsistent after schema migration. We recommend that you evaluate the impact of data type conversion on your business. For more information, see Data type mappings between heterogeneous databases.
Full data migration	DTS migrates the existing data of the required objects from the self-managed Oracle database to the destination database.
Incremental data migration	After full data migration is complete, DTS retrieves redo log files from the self-managed Oracle database. Then, DTS migrates incremental data from the self-managed Oracle database to the destination database. Incremental data migration ensures service continuity of self-managed applications during data migration.

SQL operations that can be incrementally migrated

Operation type	SQL statement
DML	INSERT, UPDATE, and DELETE
DDL	CREATE TABLE Note DTS does not migrate the CREATE TABLE operations that are performed to create tables in which functions are nested. ALTER TABLE, ADD COLUMN, DROP COLUMN, RENAME COLUMN, and ADD INDEX DROP TABLE RENAME TABLE, TRUNCATE TABLE, and CREATE INDEX Note Only the CREATE INDEX operations that are performed within the current database account can be migrated.

Data type mappings

For more information, see Data type mappings between heterogeneous databases.

Preparations

Log on to the self-managed Oracle database, create an account that you want to use to collect data, and then grant permissions to the account.

Note

If you have created an account that is granted the permissions listed in the following table, you can skip this step.

Database	Schema migration	Full data migration	Incremental data migration
Self-managed Oracle database	Permissions of the schema owner	Permissions of the schema owner	Fine-grained permissions
ApsaraDB RDS for MySQL instance	The write permissions on the destination database

To create a database account and grant permissions to the database account, perform the following operations:

Self-managed Oracle database: CREATE USER and GRANT.
ApsaraDB RDS for MySQL instance: Create an account and Modify the permissions of an account.

Important

If you need to migrate incremental data, you also need to enable archiving and supplementary logging to obtain incremental changes to the data. For more information, please refer to Configure an Oracle database.

Procedure

Go to the Data Migration Tasks page.
1. Log on to the Data Management (DMS) console.
2. In the top navigation bar, click DTS.
3. In the left-side navigation pane, choose DTS (DTS) > Data Migration.
Note
- Operations may vary based on the mode and layout of the DMS console. For more information, see Simple mode and Customize the layout and style of the DMS console.
- You can also go to the Data Migration Tasks page of the new DTS console.
From the drop-down list next to Data Migration Tasks, select the region in which the data migration instance resides.
Note
If you use the new DTS console, you must select the region in which the data migration instance resides in the upper-left corner.

Click Create Task. In the Create Task wizard, configure the source and destination databases.

Warning

After you configure the source and destination databases, we recommend that you read the limits that are displayed in the upper part of the page. Otherwise, the task may fail or data inconsistency may occur.

Section	Parameter	Description
N/A	Task Name	The name of the task. DTS automatically assigns a name to the task. We recommend that you specify a descriptive name that makes it easy to identify the task. You do not need to specify a unique task name.
Source Database	Database Type	The type of the source database. Select Oracle.
	Access Method	The access method of the source database. In this example, Public IP Address is selected. Note If you select other access methods, you must set up the environment that is required for the self-managed Oracle database. For more information, see Preparation overview.
	Instance Region	The region in which the source Oracle database resides.
	Hostname or IP address	The endpoint that is used to connect to the self-managed Oracle database.
	Port Number	The service port number of the self-managed Oracle database. Default value: 1521. Note In this example, the service port of the self-managed Oracle database must be accessible over the Internet.
	Oracle Type	The architecture of the source Oracle database. If you select Non-RAC Instance, you must configure the SID parameter. If you select RAC or PDB Instance, you must configure the Service Name parameter. In this example, Non-RAC Instance is selected.
	Database Account	The account of the source Oracle database. For more information about the permissions that are required for the account, see the Preparations section of this topic.
	Database Password	The password of the database account.
Destination Database	Database Type	The type of the destination database. Select MySQL.
	Access Method	The access method of the destination database. Select Alibaba Cloud Instance.
	Instance Region	The region in which the destination ApsaraDB RDS for MySQL instance resides.
	RDS Instance ID	The ID of the destination ApsaraDB RDS for MySQL instance.
	Database Account	The database account of the destination ApsaraDB RDS for MySQL instance. For more information about the permissions that are required for the account, see the Preparations section of this topic.
	Database Password	The password of the database account.
	Encryption	Specifies whether to encrypt the connection to the source database instance. Select Non-encrypted or SSL-encrypted based on your business requirements. If you select SSL-encrypted, you must enable SSL encryption for the ApsaraDB RDS for MySQL instance before you configure the data migration task. For more information, see Configure the SSL encryption feature.

If an IP address whitelist is configured for your self-managed database, add the CIDR blocks of DTS servers to the IP address whitelist. Then, click Test Connectivity and Proceed.
Warning
If the public CIDR blocks of DTS servers are automatically or manually added to the whitelist of a database instance or to the security group rules of an ECS instance, security risks may arise. Therefore, before you use DTS to migrate data, you must understand and acknowledge the potential risks and take preventive measures, including but not limited to the following measures: enhancing the security of your username and password, limiting the ports that are exposed, authenticating API calls, regularly checking the whitelist or security group rules and forbidding unauthorized CIDR blocks, or connecting the database instance to DTS by using Express Connect, VPN Gateway, or Smart Access Gateway.

Configure the objects to be migrated and advanced settings.

Parameter	Description
Migration Types	To perform only full data migration, select Schema Migration and Full Data Migration. To ensure service continuity during data migration, select Schema Migration, Full Data Migration, and Incremental Data Migration. Note If you do not select Incremental Data Migration, we recommend that you do not write data to the source database during data migration. This ensures data consistency between the source and destination databases.
Processing Mode of Conflicting Tables	Precheck and Report Errors: checks whether the destination database contains tables that use the same names as tables in the source database. If the source and destination databases do not contain tables that have identical table names, the precheck is passed. Otherwise, an error is returned during the precheck and the data migration task cannot be started. Note If the source and destination databases contain identical table names and the tables in the destination database cannot be deleted or renamed, you can use the object name mapping feature to rename the tables that are migrated to the destination database. For more information, see Map object names. Ignore Errors and Proceed: skips the precheck for identical table names in the source and destination databases. Warning If you select Ignore Errors and Proceed, data inconsistency may occur and your business may be exposed to the following potential risks: If the source and destination databases have the same schema, DTS does not migrate data records that have the same primary keys as data records in the destination database. If the source and destination databases have different schemas, only specific columns are migrated or the data migration task fails. Proceed with caution.
Source Objects	Select one or more objects from the Source Objects section and click the icon to add the objects to the Selected Objects section.
Selected Objects	To rename an object that you want to migrate to the destination instance, right-click the object in the Selected Objects section. For more information, see Map the name of a single object. To rename multiple objects at a time, click Batch Edit in the upper-right corner of the Selected Objects section. For more information, see Map multiple object names at a time. Note If you use the object name mapping feature to rename an object, other objects that depend on the object may fail to be migrated. To specify WHERE conditions to filter data, right-click a table in the Selected Objects section. In the dialog box that appears, specify the conditions. For more information, see Set filter conditions. To incrementally migrate SQL operations performed on a specific database or table, right-click the object in the Selected Objects section. In the dialog box that appears, select the SQL operations that you want to incrementally migrate. For more information about the SQL statements that can be incrementally migrated, see the SQL operations that can be incrementally migrated section of this topic.

Click Next: Advanced Settings to configure advanced settings.

Data Verification Settings
For more information about how to use the data verification feature, see Configure data verification.

Advanced Settings

Parameter	Description
Select the dedicated cluster used to schedule the task	By default, DTS schedules the task to a shared cluster. You do not need to configure this parameter. You can also purchase and specify a dedicated cluster of the required specifications to run the data migration task. For more information, see What is a DTS dedicated cluster.
Retry Time for Failed Connections	The retry time range for failed connections. If the source or destination database fails to be connected after the data migration task is started, DTS immediately retries a connection within the retry time range. Valid values: 10 to 1440. Unit: minutes. Default value: 720. We recommend that you set the parameter to a value greater than 30. If DTS is reconnected to the source and destination databases within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration task fails. Note If you specify different retry time ranges for multiple data migration tasks that share the same source or destination database, the value that is specified later takes precedence. When DTS retries a connection, you are charged for the DTS instance. We recommend that you specify the retry time range based on your business requirements. You can also release the DTS instance at the earliest opportunity after the source database and destination instance are released.
The wait time before a retry when other issues occur in the source and destination databases.	The retry time range for other issues. For example, if DDL or DML operations fail to be performed after the data migration task is started, DTS immediately retries the operations within the retry time range. Valid values: 1 to 1440. Unit: minutes. Default value: 10. We recommend that you set the parameter to a value greater than 10. If the failed operations are successfully performed within the specified retry time range, DTS resumes the data migration task. Otherwise, the data migration task fails. Important The value of the The wait time before a retry when other issues occur in the source and destination databases parameter must be smaller than the value of the Retry Time for Failed Connections parameter.
Enable Throttling for Full Data Migration	Specifies whether to enable throttling for full data migration. During full data migration, DTS uses the read and write resources of the source and destination databases. This may increase the loads of the database servers. You can enable throttling for full data migration based on your business requirements. To configure throttling, you must configure the Queries per second (QPS) to the source database, RPS of Full Data Migration, and Data migration speed for full migration (MB/s) parameters. This reduces the loads of the destination database server. Note You can configure this parameter only when you select Full Data Migration for the Migration Types parameter.
Enable Throttling for Incremental Data Migration	Specifies whether to enable throttling for incremental data migration. To configure throttling, you must configure the RPS of Incremental Data Migration and Data migration speed for incremental migration (MB/s) parameters. This reduces the loads of the destination database server. Note You can configure this parameter only when you select Incremental Data Migration for the Migration Types parameter.
Environment Tag	The environment tag that is used to identify the DTS instance. You can select an environment tag based on your business requirements. In this example, no environment tag is added.
Actual Write Code	The encoding format in which data is written to the destination database. Select an encoding format based on your business requirements.
Configure ETL	Specifies whether to enable the extract, transform, and load (ETL) feature. For more information, see What is ETL? Valid values: Yes: configures the ETL feature. You can enter data processing statements in the code editor. For more information, see Configure ETL in a data migration or data synchronization task. No: does not configure the ETL feature.
Monitoring and Alerting	Specifies whether to configure alerting for the data migration task. If the task fails or the migration latency exceeds the specified threshold, the alert contacts receive notifications. Valid values: No: does not configure alerting. Yes: configures alerting. If you select Yes, you must also specify the alert threshold and alert contacts. For more information, see the Configure monitoring and alerting for a new DTS task section of the "Configure monitoring and alerting" topic.

In the lower part of the page, click Next: Save Task Settings and Precheck.
You can move the pointer over Next: Save Task Settings and Precheck and click Preview API Call to view the parameter settings of the API operation that is called to configure the instance.
Note
- Before you can start the data migration task, DTS performs a precheck. You can start the data migration task only after the task passes the precheck.
- If the task fails to pass the precheck, click View Details next to each failed item. After you troubleshoot the issues based on the causes, run a precheck again.
- If an alert is generated for an item during the precheck, perform the following operations based on the scenario:
  If the alert item cannot be ignored, click View Details next to the failed item and troubleshoot the issues. Then, run a precheck again.
  If the alert item can be ignored, click Confirm Alert Details. In the View Details dialog box, click Ignore. In the message that appears, click OK. Then, click Precheck Again to run a precheck again. If you ignore the alert item, data inconsistency may occur and your business may be exposed to potential risks.
Wait until the success rate becomes 100%. Then, click Next: Purchase Instance.
Read and agree to Data Transmission Service (Pay-as-you-go) Service Terms by selecting the check box.
Click Buy and Start to start the data migration task. You can view the progress of the task on the Task Management page of the data migration task.