Using a MySQL-compatible database as a target for Amazon Database Migration Service - Amazon Database Migration Service
Prerequisites for MySQL as a targetLimitations on MySQL as a targetEndpoint settingsTarget data types for MySQL
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Using a MySQL-compatible database as a target for Amazon Database Migration Service

You can migrate data to any MySQL-compatible database using Amazon DMS, from any of the source data engines that Amazon DMS supports. If you are migrating to an on-premises MySQL-compatible database, then Amazon DMS requires that your source engine reside within the Amazon ecosystem. The engine can be on an Amazon-managed service such as Amazon RDS, Amazon Aurora, or Amazon S3. Or the engine can be on a self-managed database on Amazon EC2.

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 Amazon Database Migration Service.

For information about versions of MySQL that Amazon DMS supports as a target, see Targets for Amazon DMS.

You can use the following MySQL-compatible databases as targets for Amazon DMS:

  • MySQL Community Edition

  • MySQL Standard Edition

  • MySQL Enterprise Edition

  • MySQL Cluster Carrier Grade Edition

  • MariaDB Community Edition

  • MariaDB Enterprise Edition

  • MariaDB Column Store

  • Amazon Aurora MySQL

Note

Regardless of the source storage engine (MyISAM, MEMORY, and so on), Amazon DMS creates a MySQL-compatible target table as an InnoDB table by default.

If you need a table in a storage engine other than InnoDB, you can manually create the table on the MySQL-compatible target and migrate the table using the Do nothing option. For more information, see Full-load task settings.

For additional details on working with a MySQL-compatible database as a target for Amazon DMS, see the following sections.

Using any MySQL-compatible database as a target for Amazon Database Migration Service

Before you begin to work with a MySQL-compatible database as a target for Amazon DMS, make sure that you have completed the following prerequisites:

  • Provide a user account to Amazon DMS that has read/write privileges to the MySQL-compatible database. To create the necessary privileges, run the following commands.

    
CREATE USER '<user acct>'@'%' IDENTIFIED BY '<user password>';
GRANT ALTER, CREATE, DROP, INDEX, INSERT, UPDATE, DELETE, SELECT ON <schema>.* TO 
'<user acct>'@'%';
GRANT ALL PRIVILEGES ON awsdms_control.* TO '<user acct>'@'%';

  • During the full-load migration phase, you must disable foreign keys on your target tables. To disable foreign key checks on a MySQL-compatible database during a full load, you can add the following command to the Extra connection attributes section of the Amazon DMS console for your target endpoint.

    Initstmt=SET FOREIGN_KEY_CHECKS=0;

  • Set the database parameter local_infile = 1 to enable Amazon DMS to load data into the target database.

Limitations on using a MySQL-compatible database as a target for Amazon Database Migration Service

When using a MySQL database as a target, Amazon DMS doesn't support the following:

  • The data definition language (DDL) statements TRUNCATE PARTITION, DROP TABLE, and RENAME TABLE.

  • Using an ALTER TABLE table_name ADD COLUMN column_name statement to add columns to the beginning or the middle of a table.

  • When loading data to a MySQL-compatible target in a full load task, Amazon DMS doesn't report errors caused by constraints in the task logs, which can cause duplicate key errors or mismatches with the number of records. This is caused by the way MySQL handles local data with the LOAD DATA command. Be sure to do the following during the full load phase:

    • Disable constraints

    • Use Amazon DMS validation to make sure the data is consistent.

  • When you update a column's value to its existing value, MySQL-compatible databases return a 0 rows affected warning. Although this behavior isn't technically an error, it is different from how the situation is handled by other database engines. For example, Oracle performs an update of one row. For MySQL-compatible databases, Amazon DMS generates an entry in the awsdms_apply_exceptions control table and logs the following warning.

    
Some changes from the source database had no impact when applied to
the target database. See awsdms_apply_exceptions table for details.

  • Aurora Serverless is available as a target for Amazon Aurora version 2, compatible with MySQL version 5.7. (Select Aurora MySQL version 2.07.1 to be able to use Aurora Serverless with MySQL 5.7 compatibility.) For more information about Aurora Serverless, see Using Aurora Serverless v2 in the Amazon Aurora User Guide.

  • Amazon DMS doesn't support using a reader endpoint for Aurora or Amazon RDS, unless the instances are in writable mode, that is, the read_only and innodb_read_only parameters are set to 0 or OFF. For more information about using Amazon RDS and Aurora as targets, see the following:

Endpoint settings when using a MySQL-compatible database as a target for Amazon DMS

You can use endpoint settings to configure your MySQL-compatible target database similar to using extra connection attributes. You specify the settings when you create the target endpoint using the Amazon DMS console, or by using the create-endpoint command in the Amazon CLI, with the --my-sql-settings '{"EndpointSetting": "value", ...}' JSON syntax.

The following table shows the endpoint settings that you can use with MySQL as a target.

Name Description

TargetDbType

Specifies where to migrate source tables on the target, either to a single database or multiple databases. If you specify SPECIFIC_DATABASE, you need to specify the database name, either when using the Amazon CLI or the Amazon Web Services Management Console.

Default value: MULTIPLE_DATABASES

Valid values: {SPECIFIC_DATABASE, MULTIPLE_DATABASES}

Example: --my-sql-settings '{"TargetDbType": "MULTIPLE_DATABASES"}'

ParallelLoadThreads

Improves performance when loading data into the MySQL-compatible target database. Specifies how many threads to use to load the data into the MySQL-compatible target database. Setting a large number of threads can have an adverse effect on database performance, because a separate connection is required for each thread.

Default value: 1

Valid values: 1–5

Example: --my-sql-settings '{"ParallelLoadThreads": 1}'

AfterConnectScript

Specifies a script to run immediately after Amazon DMS connects to the endpoint.

For example, you can specify that the MySQL-compatible target should translate received statements into the latin1 character set, which is the default compiled-in character set of the database. This parameter typically improves performance when converting from UTF8 clients.

Example: --my-sql-settings '{"AfterConnectScript": "SET character_set_connection='latin1'"}'

MaxFileSize

Specifies the maximum size (in KB) of any .csv file used to transfer data to a MySQL-compatible database.

Default value: 32,768 KB (32 MB)

Valid values: 1–1,048,576

--my-sql-settings '{"MaxFileSize": 512}'

CleanSrcMetadataOnMismatch

Cleans and recreates table metadata information on the replication instance when a mismatch occurs. An example is a situation where running an alter DDL statement on a table might result in different information about the table cached in the replication instance. Boolean.

Default value: false

Example: --my-sql-settings '{"CleanSrcMetadataOnMismatch": false}'

You can also use extra connection attributes to configure your MySQL-compatible target database.

The following table shows the extra connection attributes that you can use with MySQL as a target.

Name Description

Initstmt=SET FOREIGN_KEY_CHECKS=0;

Disables foreign key checks.

Example: --extra-connection-attributes "Initstmt=SET FOREIGN_KEY_CHECKS=0;"

Initstmt=SET time_zone

Specifies the time zone for the target MySQL-compatible database.

Default value: UTC

Valid values: The time zone names available in the target MySQL database.

Example: --extra-connection-attributes "Initstmt=SET time_zone=US/Pacific;"

Alternatively, you can use the AfterConnectScript parameter of the --my-sql-settings command to disable foreign key checks and specify the time zone for your database.

Target data types for MySQL

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

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

Amazon DMS data types

MySQL data types

BOOLEAN

BOOLEAN

BYTES

If the length is from 1 through 65,535, then use VARBINARY (length).

If the length is from 65,536 through 2,147,483,647, then use LONGLOB.

DATE

DATE

TIME

TIME

TIMESTAMP

"If scale is => 0 and =< 6, then: DATETIME (Scale)

If scale is => 7 and =< 9, then: VARCHAR (37)"

INT1

TINYINT

INT2

SMALLINT

INT4

INTEGER

INT8

BIGINT

NUMERIC

DECIMAL (p,s)

REAL4

FLOAT

REAL8

DOUBLE PRECISION

STRING

If the length is from 1 through 21,845, then use VARCHAR (length).

If the length is from 21,846 through 2,147,483,647, then use LONGTEXT.

UINT1

UNSIGNED TINYINT

UINT2

UNSIGNED SMALLINT

UINT4

UNSIGNED INTEGER

UINT8

UNSIGNED BIGINT

WSTRING

If the length is from 1 through 32,767, then use VARCHAR (length).

If the length is from 32,768 through 2,147,483,647, then use LONGTEXT.

BLOB

If the length is from 1 through 65,535, then use BLOB.

If the length is from 65,536 through 2,147,483,647, then use LONGBLOB.

If the length is 0, then use LONGBLOB (full LOB support).

NCLOB

If the length is from 1 through 65,535, then use TEXT.

If the length is from 65,536 through 2,147,483,647, then use LONGTEXT with ucs2 for CHARACTER SET.

If the length is 0, then use LONGTEXT (full LOB support) with ucs2 for CHARACTER SET.

CLOB

If the length is from 1 through 65,535, then use TEXT.

If the length is from 65,536 through 2147483647, then use LONGTEXT.

If the length is 0, then use LONGTEXT (full LOB support).