DMS FULL LOAD ERROR column value is NULL, use user defined NULL value attNULL

This error message you're encountering during your AWS Database Migration Service (DMS) full load from on-premises PostgreSQL to Aurora PostgreSQL is related to how DMS is handling NULL values in your data.

The message "column value is NULL, use user defined NULL value attNULL" is not necessarily an error, but rather an informational log. It's indicating that DMS has encountered a NULL value in a column and is using a predefined NULL value representation (in this case, "attNULL") to handle it during the migration process.

This behavior is part of DMS's normal operation when dealing with NULL values. However, the fact that your migration has been running for over 24 hours suggests there might be performance issues or other factors slowing down the process.

To address this situation:

1. Check the size of your data: If you're migrating a large amount of data, it's not uncommon for the process to take a long time.

2. Review your DMS task settings: Ensure you've configured appropriate settings for your migration, such as batch size and number of parallel load threads.

3. Monitor your source and target database performance: High load on either end can slow down the migration process.

4. Consider using the Enhanced Full Load Performance feature: If you're not already using it, this feature can significantly improve the speed of full load operations by automatically implementing parallel data loading.

5. Check for any network issues between your source and target databases that might be causing slowdowns.

6. Review the table structures: If you have tables with a large number of columns or complex data types, this can impact migration speed.

If the issue persists, you may want to consider breaking your migration into smaller chunks or reaching out to AWS Support for more detailed troubleshooting assistance.
Sources
Enhanced Full Load Performance in AWS DMS Serverless | AWS Database Blog

Please note this is a debug message ]D: you might have enabled detailed debug for component TARGET_LOAD and thus getting this verbose logging. unless it is required for troubleshooting you can reduce the logging to normal.