Hello ravishax,
As you mentioned that all these records will be pulled from a 3rd party application and then will be created in D365 automatically; therefore you can decide at what recurrence these records will updated in D365. It could be end of the day or in every 5-10 minutes depending on requirement of the client.
1. User should not be able to create records directly in d365. once user clicks new or "ALT+N"it should throw error "create a customer from "third party application"". --- I think no need to create any additional customization in this regard because you can simply control this through available standard roles and privileges in D365 as mentioned by Nikolaos.
2. User should not be able to delete records directly in d365. once user clicks new or "ALT+Delete"it should throw error "records created from "third party application" cannot be deleted". --- This is same as the 1st point. Can be controlled this through available standard roles and privileges in D365.
3. there will not be direct records from d365, so technically all the records cannot be deleted. --- Whatever the applications you are using to bring all these data in D365 from the 3rd party application; simply set the recurrence as highlighted above. Therefore; whenever you are creating, updating or even deleting any such record in that 3rd party system; D365 will be automatically updated based on the recurrence as you set.
4. edit /update will also be triggered from external systems mostly. but few records might be updated from d365 side as well. --- Same as point no. 3
Kindly check and let us know for any further concern you have on this.
Best regards,
Sourav Dam
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