Using S3 as a DMS Target

These are the specific steps I completed to get a DMS job to use Amazon s3 as a  DMS target . As well as the mechanics for creating a DMS Migration Job targeting an RDBMS as a source server and S3 as target - you should also consider Performance. 

Multiple factors influence the throughput - for some extra guidance on DMS performance - read -How can I speed up my DMS migration ?

For the purposes of these notes - I used the name "sql-to-s3" 

Use the  Amazon S3 console,  create a bucket. 

    -> Created a new bucket "sql-to-s3"
Select the bucket that you created, and then choose Create folder.

    -> Created a new folder "sql-db-target"
Enter a folder name, and then choose Save.

Create an IAM policy   (replace "bucket" ) with the bucket name created. This policy forms the basis for the DMS task to interact with the target s3 bucket 

-> Created a new policy called "sql-to-s3"

This policy definition was copied from AWS documentation, check link below in background reading 

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "s3:PutObject",
        "s3:DeleteObject",
        "s3:PutObjectTagging"
      ],
      "Resource": [
        "arn:aws:s3:::bucketname/*"
      ]
    },
    {
      "Effect": "Allow",
      "Action": [
        "s3:ListBucket"
      ],
      "Resource": [
        "arn:aws:s3:::bucketname*"
      ]
    }
  ]
}

Create a new IAM role & attach the IAM policy 

--> Choose "DMS" as the service

--> Attached the IAM policy "sql-to-s3" to a new IAM role called "sql-to-s3"

--> Make a note of the ARN associated with new IAM role. It will be required for the Target Endpoint configuration

arn:aws:iam::12731263633:role/sql-to-s3

Create your DMS target endpoint to s3 

Open the AWS DMS console, and then choose Endpoints from the navigation pane.
Choose Create endpoint, and then select Target endpoint.

--> Created an endpoint called "sql-to-s3"
Enter the Endpoint identifier, and then choose Amazon S3 as the Target engine.

-->Added "sql-to-s3" and select Amazon s3 as target engine 
Paste the Role ARN that you copied into the Service Access Role ARN field.

--> Added "arn:aws:iam::12731263633:role/sql-to-s3"
Enter a Bucket name and Bucket folder.

--> Added "sql-to-s3" for both 
Under Endpoint settings, add your Endpoint settings, if you have any. For more information, see Endpoint settings when using Amazon S3 as a target for AWS DMS.

--> Executed a connection test and got an error message -

Test Endpoint failed: Application-Status: 1020912, Application-Message: Failed to connect to database.

This link has a step by step troubleshooting guide. The troubleshooting will take you through the essential steps required . 

How can I troubleshoot Amazon S3 endpoint connection test failures when using AWS DMS?

for my specific problem - I checked through all the points and finally arrived at the passage related to :

Create VPC endpoints so that your replication instance can access all source and target endpoints that are used by AWS DMS. For more information,

I investigated the VPC endpoint related to the s3 service , checked through the details and identified a number of contradictions related to the access restrictions for the s3 service.

Once I adjsuted the restricted access via the Policy associated to the VPC endpoint , I was then able to create a successfull Test connection from DMS to s3

Some background reading 

Can I use an Amazon S3 bucket as an AWS DMS target?

Using security socket layer (SSL) on DMS Endpoints