Understanding immutable keys

In Dynamics 365 Business Central, all tables have a (unique) immutable key (a GUID field) that can be used for integration scenarios and for replacing the old RECORDID property. This field is called SystemId and it's a GUID data type field that specifies a unique, immutable (read-only) identifier for records in a table.The SystemId field (identified with the field number 2000000000 on every table object) has the following characteristics:

• It has a value for every record in a table.
• You can assign a value at insert time; otherwise, the platform automatically assigns one.
• Once SystemId has been set, it cannot be changed.
• There is always a unique secondary key in the SystemId field.

As a platform rule, modifying SystemId of an existing record is not allowed. The INSERT function has an override method for handling the SystemId:

Record.Insert([RunTrigger: Boolean[, InsertWithSystemId: Boolean]])

SystemId can be manually specified when inserting a new record...