GlobalID

A field of type UUID (Universal Unique Identifier) in which values are automatically assigned by the geodatabase when a table row is created. The GlobalID field is necessary for maintaining object uniqueness across replicas. All feature classes and tables participating in one-way or two-way replication must contain the GlobalID field. This field is not editable and is automatically populated when it is added for existing data. A GlobalID is often used as the primary key in the database table, but it is different than the typical OBJECTID or FID field. A GlobalID is often created in ArcGIS by right-clicking in the ArcCatalog tree and choosing "Add Global IDs". It can be applied to standalone feature classes or tables, or applied to an entire feature dataset.