Assistance Required to Restore .BAK File from S3 to RDS for SQL Server

To restore a .bak file from Amazon S3 to your RDS instance for Microsoft SQL Server, you'll need to follow these steps:

1. Ensure that your RDS instance has the SQLSERVER_BACKUP_RESTORE option added to its option group. This option is required for native backup and restore operations.

2. Make sure the IAM role associated with your RDS instance has the necessary permissions to access the S3 bucket containing your backup file. The role should have both read and list permissions for the S3 bucket.

3. Verify that the S3 bucket containing your backup file is in the same AWS region as your RDS instance, as cross-region restores are not supported.

4. To restore the database, you'll need to use the rds_restore_database stored procedure. You can execute this procedure using either DBeaver or MSSQL Management Studio. Here's an example of how to use the stored procedure:

   exec msdb.dbo.rds_restore_database @restore_db_name='YourDatabaseName', @s3_arn_to_restore_from='arn:aws:s3:::YourBucketName/YourBackupFileName.bak';

   Replace 'YourDatabaseName' with the name you want to give the restored database, and adjust the S3 ARN to match your bucket and file name.

5. After executing the stored procedure, you can check the status of the restore task using the rds_task_status stored procedure:

   exec msdb.dbo.rds_task_status @db_name='YourDatabaseName';

6. The restore process may take some time depending on the size of your backup file. Once completed, you should see your restored database in your RDS instance.

Remember that you can only run up to two backup or restore tasks simultaneously on your RDS instance. Also, ensure that your backup file doesn't exceed the 5 TB size limit for S3 objects.

If you encounter any "Forbidden" errors during the restore process, double-check your IAM role permissions and S3 bucket policies. Also, if your RDS instance is encrypted, make sure you've provided the necessary KMS key permissions in the IAM role.

By following these steps, you should be able to successfully restore your .bak file from S3 to your RDS for SQL Server instance.
Sources
Restore SQL bak backupfile to RDS Database | AWS re:Post
Importing and exporting SQL Server databases using native backup and restore - Amazon Relational Database Service