This topic describes how to migrate data from an Amazon RDS for Oracle instance 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 configure a data migration task, you can select all of the supported migration types to ensure service continuity.
Prerequisites
- The Public accessibility option of the Amazon RDS for Oracle instance is set to Yes. The setting ensures that DTS can access the Amazon RDS for Oracle instance over the Internet.
- The database version of the Amazon RDS for Oracle instance is 9i, 10g, 11g, or 12c or later (non-multitenant architecture).
- The database version of the ApsaraDB RDS for MySQL instance is 5.6 or 5.7.
- The available storage space of the ApsaraDB RDS for MySQL instance is at least twice
the total size of the data in the Amazon RDS for Oracle instance.
Note The binary log files that are generated during data migration occupy some space. They are automatically cleared after data migration is complete.
Precautions
- DTS uses read and write resources of the source and destination databases during full data migration. This may increase the loads of the database servers. If the database performance is unfavorable, the specification is low, or the data volume is large, database services may become unavailable. For example, DTS occupies a large amount of read and write resources in the following cases: a large number of slow SQL queries are performed on the source database, the tables have no primary keys, or a deadlock occurs in the destination database. Before you migrate data, evaluate the impact of data migration on the performance of the source and destination databases. We recommend that you migrate data during off-peak hours. For example, you can migrate data when the CPU utilization of the source and destination databases is less than 30%.
- The tables to be migrated in the source database must have PRIMARY KEY or UNIQUE constraints and all fields must be unique. Otherwise, the destination database may contain duplicate data records.
- DTS uses the
ROUND(COLUMN,PRECISION)
function to retrieve values from columns of the FLOAT or DOUBLE data type. If you do not specify a precision, DTS sets the precision for the FLOAT data type to 38 digits and the precision for the DOUBLE data type to 308 digits. You must check whether the precision settings meet your business requirements. - 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 manually create a
database in the ApsaraDB RDS for MySQL instance before you configure the data migration
task.
Note For more information about the naming conventions of ApsaraDB RDS for MySQL databases and how to create a database, see Create a database on an ApsaraDB RDS for MySQL instance.
- If a data migration task fails, DTS automatically resumes the task. Before you switch your workloads to the destination instance, stop or release the data migration task. Otherwise, the data in the source instance will overwrite the data in the destination instance after the task is resumed.
Billing
Migration type | Task 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
- Schema migration
DTS supports schema migration for the following types of objects: table, index, constraint, and sequence. DTS does not support schema migration for the following types of objects: view, synonym, trigger, stored procedure, function, package, and user-defined type.
- Full data migration
DTS migrates historical data of the required objects from the source database in the Amazon RDS for Oracle instance to the destination database in the ApsaraDB RDS for MySQL instance.
- Incremental data migration
DTS retrieves redo log files from the source database in the Amazon RDS for Oracle instance. Then, DTS synchronizes incremental data from the source database in the Amazon RDS for Oracle instance to the destination database in the ApsaraDB RDS for MySQL instance. Incremental data migration allows you to ensure service continuity when you migrate data from an Oracle database.
SQL operations that can be synchronized during incremental data migration
- INSERT, DELETE, and UPDATE
- CREATE TABLE
Note If a CREATE TABLE operation creates a partitioned table or a table that contains functions, DTS does not synchronize the operation.
- ALTER TABLE, including only ADD COLUMN, DROP COLUMN, RENAME COLUMN, and ADD INDEX
- DROP TABLE
- RENAME TABLE, TRUNCATE TABLE, and CREATE INDEX
Permissions required for database accounts
Database | Schema migration | Full data migration | Incremental data migration |
---|---|---|---|
Amazon RDS for Oracle instance | The permissions of the schema owner | The permissions of the schema owner | The permissions of the master user |
ApsaraDB RDS for MySQL instance | The read and write permissions on the destination database | The read and write permissions on the destination database | The read and write permissions on the destination database |
For more information about how to create and authorize database account, see the following topics:
- Amazon RDS for Oracle instance: CREATE USER and GRANT
- ApsaraDB RDS for MySQL instance: Create accounts and databases for an ApsaraDB RDS for MySQL instance
Data type mappings
For more information, see Data type mappings between heterogeneous databases.