DMS Serverless - Internal server error

Based on your description, you're experiencing an internal server error with your AWS DMS Serverless replication task. Since you mentioned that two tasks are already running successfully with one database, but the third task with a different database is failing, this suggests a configuration issue specific to that database connection.

When DMS Serverless replication fails with an internal server error and limited logs, there are several potential causes to investigate:

1. Endpoint Connection Issues: The most common cause is a failure to connect to the source or target endpoint. DMS Serverless replications don't have public IP addresses for management tasks, so if your endpoints are in different VPCs, you need proper connectivity between them.

2. VPC Endpoint Configuration: Since you mentioned DMS is in one VPC and Redshift Serverless is in another, verify that you have proper VPC connectivity between them. For DMS Serverless, a VPC endpoint is often required for cross-VPC communication.

3. Subnet Group Configuration: Ensure that your DMS replication subnet group includes subnets that can access both your source database and Redshift target.

4. IAM Roles and Permissions: Verify that the IAM roles associated with your DMS task have the necessary permissions to access the new database.

5. Database-Specific Configuration: Since the issue is specific to one database while others work, check if there are any unique settings, schema differences, or access restrictions on this particular database.

To troubleshoot:

• Test the endpoints individually to ensure they're configured correctly
• Check CloudWatch logs for more detailed error messages
• Verify network connectivity between the VPCs
• Ensure your replication subnet group is properly configured
• Check that IAM roles have appropriate permissions

If the error persists with limited logs, you might need to create a new replication configuration with more detailed logging enabled to better diagnose the issue.
Sources
How to Solve This Error in AWS DMS Serverless? | AWS re:Post
AWS DMS Serverless components - AWS Database Migration Service
Replication - AWS Database Migration Service