What exactly version are you using? 9.0 had about a dozed maintenance releases so far.
In any case - looks like you are hitting a product issue. I'll look up tomorrow if or when was it addressed and if there is a workaround for this.
Could you fell me what are you connecting to?
Also, do you already have an extract and want to convert to incremental one?
I have already have an extract and want to convert to incremental one, but I followed the process to have a incremental refresh, it didn't work.
Could you pls kindly to tell me how to have a incremental one?
when I have the incremental refresh, it will be easier for my tableau server to refresh database.
BTW, now I use the version 9.3.6.
What steps do you follow and what exactly problems are you experiencing?
This guide is pretty good: Quick Start: Incremental Extract Updates
One requirement that incremental extracts have is that your data should either have monotonously increasing whole numbers (like record id or order id) or date/datetime.