DRS supports now Migrating Data from RDS for MySQL to DDM

• On-premises databases (MySQL 5.5, 5.6, 5.7, and 8.0)
• ECS databases (MySQL 5.5, 5.6, 5.7, and 8.0)
• Other cloud databases (MySQL 5.5, 5.6, 5.7, and 8.0)
• RDS for MySQL (5.5, 5.6, 5.7, 8.0)

• DDM instances

Restrictions on the source database

• The source database names cannot contain non-ASCII characters, or the following characters: .'<`>/\"
• The source table and view names cannot contain non-ASCII characters, or the following characters: '<>/\"
• If the source database is an on-premises database and has Percona Server for MySQL 5.6.x or Percona Server for MySQL 5.7.x installed, the memory manager must use Jemalloc to prevent Out of Memory errors caused by frequent queries on system tables.
• The source database does not support the mysql binlog dump command.
• The source database does not support the reset master or reset master to command, which may cause DRS task failures or data inconsistency.
• Associated objects must be migrated at the same time to avoid migration failure caused by missing associated objects.
• Cascade operations cannot be performed on tables with foreign keys. If the foreign key index of a table is a common index, the table structure may fail to be created. You are advised to use a unique index.
• Due to the MySQL constraints, if the one-time event triggering time of the source database is earlier than the migration start time, the event will not be migrated to the destination database.

Restrictions on usage

General

• During the migration, do not modify or delete the usernames, passwords, and permissions of the source and destination databases or change the ports of the source and destination databases.
• During migration, do not modify the destination database (including but not limited to DDL and DML operations) that is being migrated.
• During migration, do not write the statement-based binlog into the source database.
• During migration, do not clear the binlog in the source database.
• During migration, do not create a database named ib_logfile in the source database.
• During the migration, do not upgrade the source MySQL database across major versions. Otherwise, data may become inconsistent or the migration task may fail (data, table structures, and keywords may cause compatibility changes after the cross-version upgrade). You are advised to create a migration task again if the source MySQL database is upgraded across major versions.

Full migration

• During task startup and full migration, do not perform DDL operations on the source database. Otherwise, the task may be abnormal.

Incremental migration

• During an incremental migration of table-level objects, renaming tables is not supported.
• During an incremental migration, do not perform the point-in-time recovery (PITR) operation on the source database.
• During an incremental migration, resumable upload is supported. However, data may be repeatedly inserted into a non-transactional table that does not have a primary key when the server system breaks down.
• During an incremental migration, the following DDL statements are supported:  AD​D COLU​MN, MODI​FY COL​UMN, CHAN​GE COL​UMN, CRE​ATE IND​EX, DRO​P IND​EX, REN​AME IND​EX and AD​D IN​DEX.

Stopping a task

• If the destination DDM version is later than 3.0.4.1, DRS automatically updates the start value of the DDM sequence when the task is complete.

Other restrictions

• When creating multiple migration tasks in the many-to-one scenario, ensure that the read and write settings of the destination database are consistent in these tasks.
• The table without a primary key lacks a unique identifier for rows. When the network is unstable, you may need to retry the task several times, or data inconsistency may occur.
• If a physically generated column in a table is generated based on a time type, the data in the column may be inconsistent.
• If Transparent Data Encryption (TDE) is enabled for the source database table, TDE must also be enabled for the destination database. Otherwise, the table structure fails to be created and the task will be abnormal.
• If the source MySQL database does not support TLS 1.2 or is a self-built database of an earlier version (earlier than 5.6.46 or between 5.7.0 and 5.7.28), you need to submit an O&M application for testing the SSL connection.
• Before creating a DRS task, if concurrency control rules of SQL statements are configured for the source database, the DRS task may fail.
• Ensure that the destination database is empty before starting the migration. Otherwise, data in the destination may be overwritten during incremental migration.
• If the destination DB instance uses columns of the TIMESTAMP or DATETIME data type as its sharding key, the seconds precision of the column is removed after the migration.