The menu option: Tools -> GAM -> Reprocess Permissions impacts the GAM permissions (which are already generated), without the need to Rebuild All of the objects in the Knowledge Base.
A use case of this Option is, for example, when there is a Knowledge Base(KB) with GAM that has certain Objects with Authorization (Objects with Integrated Security Level property: True).
If in that KB the GAM Database (DB) is changed to another existing DB, when executing the Reprocess Permissions option, the permissions that were already generated for the previous DB are impacted on the new DB.
These permissions keep the same GUID they had when generated.
GAM - Initialize Metadata option
GAM - Applications Registration option
GAM - Create tables option