Note to OP: Please click the Insert/edit code sample button when adding code to your posts, it's really not difficult to use.

I've attached the failure to this post.

I cannot see it.

Phil,

Yes, there won't be any duplication in the file within itself because of the unique values(username).

However, regular importing the same CSV file with older data and new data, will...

If the key is unique, how can there possibly...

What do you mean by 'unique values'?

The...

What do you mean by 'continuous record-appending file'? Is this a file which just keeps on growing forever? I'd be looking quite vigorously for a way to avoid that, because...

Is the user a member of the ssis_admin role in SSISDB?

Are you using a Windows login to perform the deployment? SSIS does not like SQL logins much.

Regarding your question about column names, have you considered creating a text file which contains (only) your desired column names as headings (which match the names in your target table)...

I did not quite understand your suggestion about the Data Conversion component for the columns.  I am getting CSV files with hundreds of columns.  Are you suggesting that I...

Unfortunately, the short answer is 'no and no', to the best of my knowledge.

Regarding your second point, the 'pure' SSIS way of handling this is to send all of the...

This is not the important thing. You need to look inside the...

Sounds like it is expecting (n+1) columns rather than the (n) that are there. Why not fix that, rather than modifying the input file?

Why is the final comma needed? My CSV files don't need one.

Have a look at the first answer here: https://stackoverflow.com/questions/36116795/how-to-update-a-record-in-text-file

As long as your file is not too huge, that gets you pretty close.