Multiple users saving at same time issue Oracle

Question

Hi,

 

i am using ADO.NET Transactions with oracle DB for my ASP.NET web applicaiton . When the user clicks on save button then there is a logic (oracle function) for creating a Unique ID (primary key) based on the customer type such as walkIn customer.

 

when multiple users are clicking save at the same time then for one the user system saves the data correctly (by generating the unique id)  and for the other users error is displayed with message  "Unique contrainst Violated."

 

how to fix this issue?