In System, the Reference No. field in transactions can be set as a Unique Field using the Customization Center. 


For example, the Reference No. in Sales Order wherein it will be set that the system will detect if there is a duplicate Reference No.


To set it up, go to Tools  > Customization Centre





In the User Difference, Select QNE Business Solutions so that the ruling will be applied to all users.




Under Model tab, QNE Business Solutions > Validation > Rules > Add > Rule Unique Value




Then follow the Set Ruling below;


Result Type: it should be set to Error for the system to prompt that it is an Error
TargetContextIDs: it should be set to Save so ruling will trigger upon Saving of the Transaction

TargetPropertyName: the field name in the transaction

TargetType: it specifies the type of the object for which the Validation Rule will be checked

CustomMessageTemplate: it specifies a custom informational text that is displayed in a validation error message for a broken Validation Rule

ID: it specifies the Validation Rule identifier


NOTE: CustomMessageTemplate and ID can be set differently 



In transaction, there is already a saved Sales Order with a Reference No. of 12345.



Upon creating another Sales Order with the same Reference No. that already exists, system was able to prompt the Validation Error.