DMS Sync Issues with nullable column and new columns

Question

IHAC who is facing a couple of sync issues:
Say we have a table T on mysql src db with a column C that is nullable. The table is fully loaded on the target and the DMS task is operating in CDC mode. If this table T gets altered so column C is made not nullable with a default, this change does not propagate , nor does the DMS task indicate an error.
In addition, any new columns added to table T on the source, also do not propagate. When the DMS task is operating in CDC mode, new tables that are created without a Primary Key do not propagate to the target. It can break DMS replication (error shows in logs).
Thank you

Answer

Hello,

this is a documented limitation of CDC for MySQL as a source:
https://docs.aws.amazon.com/dms/latest/userguide/CHAP_Source.MySQL.html#CHAP_Source.MySQL.Limitations

Answer

Hello,

--> In general, DMS supports below DDL:
[+] https://docs.aws.amazon.com/dms/latest/userguide/CHAP_Introduction.SupportedDDL.html

--> Using MySQL(on-prem/Aurora MySQL/RDS MySQL) as source having limitation:
"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." [+] https://docs.aws.amazon.com/dms/latest/userguide/CHAP_Source.MySQL.html#CHAP_Source.MySQL.Limitations

--> If create table or add column not working properly, will need to dive deep into the issue using DMS log with detailed debug on SOURCE_CAPTURE, TASK_MANAGER, TARGET_APPLY to check further.

Note: "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."

--> What are the target/source endpoints:

Engine version (source and target)
DMS version -- Check release note see if any known issues

--> Go through the current limitations and documentations to verify further. [+] https://docs.aws.amazon.com/dms/latest/userguide/CHAP_Source.MySQL.html

DMS Sync Issues with nullable column and new columns

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