Using a MySQL-compatible database as a source for AWS DMS

You can migrate data from any MySQL-compatible database (MySQL, MariaDB, or Amazon Aurora MySQL) using AWS Database Migration Service. MySQL versions 5.5, 5.6, 5.7, and 8.0. MariaDB versions 10.0.24 to 10.0.28, 10.1, 10.2, 10.3, 10.4, and 10.5, and also Amazon Aurora MySQL, are supported for on-premises.

Note

Support for MySQL 8.0 as a source is available in AWS DMS versions 3.4.0 and later, except when the transaction payload is compressed. AWS DMS doesn't currently support CDC replication using MySQL 8.0 as a source when binary log encryption is turned on.

You can use SSL to encrypt connections between your MySQL-compatible endpoint and the replication instance. For more information on using SSL with a MySQL-compatible endpoint, see Using SSL with AWS Database Migration Service.

In the following sections, the term "self-managed" applies to any database that is installed either on-premises or on Amazon EC2. The term "AWS-managed" applies to any database on Amazon RDS, Amazon Aurora, or Amazon S3.

For additional details on working with MySQL-compatible databases and AWS DMS, see the following sections.

Migrating from MySQL to MySQL using AWS DMS

For a heterogeneous migration, where you are migrating from a database engine other than MySQL to a MySQL database, AWS DMS is almost always the best migration tool to use. But for a homogeneous migration, where you are migrating from a MySQL database to a MySQL database, native tools can be more effective.

We recommend that you use native MySQL database migration tools such as mysqldump under the following conditions:

• You have a homogeneous migration, where you are migrating from a source MySQL database to a target MySQL database.

• You are migrating an entire database.

• The native tools allow you to migrate your data with minimal downtime.

You can import data from an existing MySQL or MariaDB database to an Amazon RDS MySQL or MariaDB DB instance. You do so by copying the database with mysqldump and piping it directly into the Amazon RDS MySQL or MariaDB DB instance. The mysqldump command-line utility is commonly used to make backups and transfer data from one MySQL or MariaDB server to another. It is included with MySQL and MariaDB client software.

For more information about importing a MySQL database into Amazon RDS for MySQL or Amazon Aurora MySQL-Compatible Edition, see Importing data into a MySQL DB instance and Importing data from a MySQL or MariaDB DB to an Amazon RDS MySQL or MariaDB DB instance.

Using AWS DMS to migrate data from MySQL to MySQL

AWS DMS can migrate data from, for example, a source MySQL database that is on premises to a target Amazon RDS for MySQL or Aurora MySQL instance. Core or basic MySQL data types most often migrate successfully.

Data types that are supported on the source database but aren't supported on the target might not migrate successfully. AWS DMS streams some data types as strings if the data type is unknown. Some data types, such as XML, can successfully migrate as small files but can fail if they are large documents.

The following table shows source MySQL data types and whether they can be migrated successfully.

Data type	Migrates successfully	Will partially migrate	Will not migrate
INT	X
BIGINT	X
MEDIUMINT	X
TINYINT	X
DECIMAL(p,s)	X
BINARY	X
BIT(M)	X
BLOB	X
LONGBLOB	X
MEDIUMBLOB	X
TINYBLOB	X
DATE	X
DATETIME	X
TIME		X
TIMESTAMP	X
YEAR	X
DOUBLE	X
FLOAT		X
VARCHAR(N)	X
VARBINARY(N)	X
CHAR(N)	X
TEXT	X
LONGTEXT	X
MEDIUMTEXT	X
TINYTEXT	X
JSON	X
GEOMETRY			X
POINT			X
LINESTRING			X
POLYGON			X
MULTILINESTRING			X
MULTIPOLYGON			X
GEOMETRYCOLLECTION			X
ENUM	X
SET	X

Using any MySQL-compatible database as a source for AWS DMS

Before you begin to work with a MySQL database as a source for AWS DMS, make sure that you have the following prerequisites. These prerequisites apply to either self-managed or AWS-managed sources.

You must have an account for AWS DMS that has the Replication Admin role. The role needs the following privileges:

• REPLICATION CLIENT – This privilege is required for CDC tasks only. In other words, full-load-only tasks don't require this privilege.

• REPLICATION SLAVE – This privilege is required for CDC tasks only. In other words, full-load-only tasks don't require this privilege.

• SUPER – This privilege is required only in MySQL versions before 5.6.6.

The AWS DMS user must also have SELECT privileges for the source tables designated for replication.

Using a self-managed MySQL-compatible database as a source for AWS DMS

You can use the following self-managed MySQL-compatible databases as sources for AWS DMS:

• MySQL Community Edition

• MySQL Standard Edition

• MySQL Enterprise Edition

• MySQL Cluster Carrier Grade Edition

• MariaDB Community Edition

• MariaDB Enterprise Edition

• MariaDB Column Store

To use CDC, make sure to enable binary logging. To enable binary logging, the following parameters must be configured in MySQL's my.ini (Windows) or my.cnf (UNIX) file.

Parameter	Value
server-id	Set this parameter to a value of 1 or greater.
log-bin	Set the path to the binary log file, such as log-bin=E:\MySql_Logs\BinLog. Don't include the file extension.
binlog_format	Set this parameter to ROW. We recommend this setting during replication because in certain cases when binlog_format is set to STATEMENT, it can cause inconsistency when replicating data to the target. The database engine also writes similar inconsistent data to the target when binlog_format is set to MIXED, because the database engine automatically switches to STATEMENT-based logging which can result in writing inconsistent data on the target database.
expire_logs_days	Set this parameter to a value of 1 or greater. To prevent overuse of disk space, we recommend that you don't use the default value of 0.
binlog_checksum	Set this parameter to NONE.
binlog_row_image	Set this parameter to FULL.
log_slave_updates	Set this parameter to TRUE if you are using a MySQL or MariaDB read-replica as a source.

If your source uses the NDB (clustered) database engine, the following parameters must be configured to enable CDC on tables that use that storage engine. Add these changes in MySQL's my.ini (Windows) or my.cnf (UNIX) file.

Parameter	Value
ndb_log_bin	Set this parameter to ON. This value ensures that changes in clustered tables are logged to the binary log.
ndb_log_update_as_write	Set this parameter to OFF. This value prevents writing UPDATE statements as INSERT statements in the binary log.
ndb_log_updated_only	Set this parameter to OFF. This value ensures that the binary log contains the entire row and not just the changed columns.

Using an AWS-managed MySQL-compatible database as a source for AWS DMS

You can use the following AWS-managed MySQL-compatible databases as sources for AWS DMS:

• MySQL Community Edition

• MariaDB Community Edition

• Amazon Aurora MySQL-Compatible Edition

When using an AWS-managed MySQL-compatible database as a source for AWS DMS, make sure that you have the following prerequisites for CDC:

• To enable binary logs for RDS for MySQL and for RDS for MariaDB, enable automatic backups at the instance level. To enable binary logs for an Aurora MySQL cluster, change the variable binlog_format in the parameter group.

  For more information about setting up automatic backups, see Working with automated backups in the Amazon RDS User Guide.

  For more information about setting up binary logging for an Amazon RDS for MySQL database, see Setting the binary logging format in the Amazon RDS User Guide.

  For more information about setting up binary logging for an Aurora MySQL cluster, see How do I turn on binary logging for my Amazon Aurora MySQL cluster?.

• If you plan to use CDC, turn on binary logging. For more information on setting up binary logging for an Amazon RDS for MySQL database, see Setting the binary logging format in the Amazon RDS User Guide.

• Ensure that the binary logs are available to AWS DMS. Because AWS-managed MySQL-compatible databases purge the binary logs as soon as possible, you should increase the length of time that the logs remain available. For example, to increase log retention to 24 hours, run the following command.

  
   call mysql.rds_set_configuration('binlog retention hours', 24);
                      

• Set the binlog_format parameter to "ROW".

  Note

  For MariaDB, if the binlog_format parameter is switched to ROW for replication purposes, subsequent binary logs are still created in MIXED format. This can prevent DMS from performing change data capture. So, when switching the binlog_format parameter for MariaDB, perform a reboot or start then stop your replication task.

• Set the binlog_row_image parameter to "Full".

• Set the binlog_checksum parameter to "NONE". For more information about setting parameters in Amazon RDS MySQL, see Working with automated backups in the Amazon RDS User Guide.

• If you are using an Amazon RDS MySQL or Amazon RDS MariaDB read replica as a source, enable backups on the read replica.

Limitations on using a MySQL database as a source for AWS DMS

When using a MySQL database as a source, consider the following:

• Change data capture (CDC) isn't supported for Amazon RDS MySQL 5.5 or lower. For Amazon RDS MySQL, you must use version 5.6 or 5.7 to enable CDC. CDC is supported for self-managed MySQL 5.5 sources.

• For CDC, CREATE TABLE, ADD COLUMN, and DROP COLUMN changing the column data type, and renaming a column are supported. However, DROP TABLE, RENAME TABLE, and updates made to other attributes, such as column default value, column nullability, character set and so on, are not supported.

• For partitioned tables on the source, when you set Target table preparation mode to Drop tables on target, AWS DMS creates a simple table without any partitions on the MySQL target. To migrate partitioned tables to a partitioned table on the target, precreate the partitioned tables on the target MySQL database.

• Using an ALTER TABLE table_name ADD COLUMN column_name statement to add columns to the beginning (FIRST) or the middle of a table (AFTER) isn't supported. Columns are always added to the end of the table.

• CDC isn't supported when a table name contains uppercase and lowercase characters, and the source engine is hosted on an operating system with case-insensitive file names. An example is Microsoft Windows or OS X using HFS+.

• You can use Aurora MySQL-Compatible Edition Serverless for full load, but you can't use it for CDC. This is because you can't enable the prerequisites for MySQL. For more information, see Parameter groups and Aurora Serverless v1.

• The AUTO_INCREMENT attribute on a column isn't migrated to a target database column.

• Capturing changes when the binary logs aren't stored on standard block storage isn't supported. For example, CDC doesn't work when the binary logs are stored on Amazon S3.

• AWS DMS creates target tables with the InnoDB storage engine by default. If you need to use a storage engine other than InnoDB, you must manually create the table and migrate to it using do nothing mode.

• You can't use Aurora MySQL replicas as a source for AWS DMS unless your DMS migration task mode is Migrate existing data—full load only.

• If the MySQL-compatible source is stopped during full load, the AWS DMS task doesn't stop with an error. The task ends successfully, but the target might be out of sync with the source. If this happens, either restart the task or reload the affected tables.

• Indexes created on a portion of a column value aren't migrated. For example, the index CREATE INDEX first_ten_chars ON customer (name(10)) isn't created on the target.

• In some cases, the task is configured to not replicate LOBs ("SupportLobs" is false in task settings or Don't include LOB columns is chosen in the task console). In these cases, AWS DMS doesn't migrate any MEDIUMBLOB, LONGBLOB, MEDIUMTEXT, and LONGTEXT columns to the target.

  BLOB, TINYBLOB, TEXT, and TINYTEXT columns aren't affected and are migrated to the target.

• Temporal data tables or system—versioned tables are not supported on MariaDB source and target databases.

• If migrating between two Amazon RDS Aurora MySQL clusters, the RDS Aurora MySQL source endpoint must be a read/write instance, not a replica instance.

• AWS DMS currently doesn't support compressed transaction log payloads introduced in MySQL 8.0.20.

• AWS DMS currently doesn't support views migration for MariaDB.

• AWS DMS doesn't support DDL changes for partitioned tables for MySQL.

• AWS DMS doesn't currently support XA transactions.

• AWS DMS doesn't support GTID for replication.

• AWS DMS doesn't support binary log transaction compression.

Extra connection attributes when using MySQL as a source for AWS DMS

You can use extra connection attributes to configure a MySQL source. You specify these settings when you create the source endpoint. If you have multiple connection attribute settings, separate them from each other by semicolons with no additional white space (for example, oneSetting;thenAnother).

The following table shows the extra connection attributes available when using Amazon RDS MySQL as a source for AWS DMS.

Name	Description
eventsPollInterval	Specifies how often to check the binary log for new changes/events when the database is idle. Default value: 5 Valid values: 1–60 Example: eventsPollInterval=5; In the example, AWS DMS checks for changes in the binary logs every five seconds.
serverTimezone	Specifies the time zone for the source MySQL database. Example: serverTimezone=US/Pacific; Don't enclose time zone data in single quotation marks.
afterConnectScript	Specifies a script to run immediately after AWS DMS connects to the endpoint. The migration task continues running regardless if the SQL statement succeeds or fails. Valid values: One or more valid SQL statements, set off by a semicolon. Example: afterConnectScript=ALTER SESSION SET CURRENT_SCHEMA = system;
CleanSrcMetadataOnMismatch	Cleans and recreates table metadata information on the replication instance when a mismatch occurs. For example, in a situation where running an alter DDL on the table could result in different information about the table cached in the replication instance. Boolean. Default value: false Example: CleanSrcMetadataOnMismatch=false;

Source data types for MySQL

The following table shows the MySQL database source data types that are supported when using AWS DMS and the default mapping from AWS DMS data types.

For information on how to view the data type that is mapped in the target, see the section for the target endpoint you are using.

For additional information about AWS DMS data types, see Data types for AWS Database Migration Service.

MySQL data types	AWS DMS data types
INT	INT4
MEDIUMINT	INT4
BIGINT	INT8
TINYINT	INT1
DECIMAL(10)	NUMERIC (10,0)
BINARY	BYTES(1)
BIT	BOOLEAN
BIT(64)	BYTES(8)
BLOB	BYTES(66535)
LONGBLOB	BLOB
MEDIUMBLOB	BLOB
TINYBLOB	BYTES(255)
DATE	DATE
DATETIME	DATETIME
TIME	STRING
TIMESTAMP	DATETIME
YEAR	INT2
DOUBLE	REAL8
FLOAT	REAL(DOUBLE) The supported FLOAT range is -1.79E+308 to -2.23E-308, 0 and 2.23E-308 to 1.79E+308 If FLOAT values aren't in this range, map the FLOAT data type to the STRING data type.
VARCHAR (45)	WSTRING (45)
VARCHAR (2000)	WSTRING (2000)
VARCHAR (4000)	WSTRING (4000)
VARBINARY (4000)	BYTES (4000)
VARBINARY (2000)	BYTES (2000)
CHAR	WSTRING
TEXT	WSTRING
JSON	NCLOB
LONGTEXT	NCLOB
MEDIUMTEXT	NCLOB
TINYTEXT	WSTRING (255)
GEOMETRY	BLOB
POINT	BLOB
LINESTRING	BLOB
POLYGON	BLOB
MULTIPOINT	BLOB
MULTILINESTRING	BLOB
MULTIPOLYGON	BLOB
GEOMETRYCOLLECTION	BLOB
ENUM	WSTRING (length) Here, length is the length of the longest value in the ENUM.
SET	WSTRING (length) Here, length is the total length of all values in the SET, including commas.

Note

In some cases, you might specify the DATETIME and TIMESTAMP data types with a "zero" value (that is, 0000-00-00). If so, make sure that the target database in the replication task supports "zero" values for the DATETIME and TIMESTAMP data types. Otherwise, these values are recorded as null on the target.