That's impossible to have 3 records with the same primary key. Primary keys are unique by nature.

I still have trouble understanding your example. Can you post what the contents of the table will look like after the appends?

>Ok, I'm using optimistic table buffering for all tables and the problem occurred during adding of new records.
>
>Example, user_A added 3 records and the primary key value is "1234", and user_B also added 3 records and primay key value is "1235".
>
>After saving, we realise that although user_A still have 3 records under key-value "1234", but the third record's data belong to those of user_B whose key value is "1235". User_B entry is ok without error.