AWS Database Migration Service
User Guide (Version API Version 2016-01-01)

Reference for AWS Database Migration Service Including Data Type Conversion Reference

This reference section includes additional information you might need when using AWS Database Migration Service (AWS DMS), including data type conversion information.

AWS DMS maintains data types when you do a homogenous database migration where both source and target use the same engine type. When you do a heterogeneous migration, where you migrate from one database engine type to a different database engine, data types are converted to an intermediate data type as shown in the table following. To see how the data types appear on the target database, consult the data type tables for the source and target database engines.

Be aware of a few important things about data types when migrating a database:

  • The UTF-8 4-byte character set (utf8mb4) isn't supported and can cause unexpected behavior in a source database. Plan to convert any data using the UTF-8 4-byte character set before migrating.

  • The FLOAT data type is inherently an approximation.

    When you insert a specific value om FLOAT, it might be represented differently in the database. This difference is because FLOAT isn't an exact data type, such as a decimal data type like NUMBER or NUMBER(p,s). As a result, the internal value of FLOAT stored in the database might be different than the value that you insert. This the migrated value of a FLOAT might not match exactly the value on the source database.

    For more information on this issue, see the following articles:

    IEEE floating point

    IEEE Floating-Point Representation

    Why Floating-Point Numbers May Lose Precision