unable to update SIT when columns marked as required

Hi

First some  background.

I have an OAF page which contains an SIT. The SIT was defined with all fields non-mandatory. The validation of data for SIT was  performed at the OAF page level and the SIT updated. It made use of hr_sit_api.update_sit function to update the SIT.

Current situation

I've now changed the SIT and made a couple of the columns mandatory. I've removed the validation logic from the OAF page and I want the SIT to perform the validation.

Now, I cannot update existing data in SIT but can add new data. It generates "Error: null"