Handling global resourcesThe system designer must identify global resources and determine mechanisms for controlling access to them.Global resources include physical units or logical units.If the unit is a physical unit, then it can control itself by using protocol for obtaining access within a concurrent system.If the unit is a logical unit, then there is a danger of conflicting access in a shared environment.Each global resources must be owned by a guardian object which controls access to it.A lock is a logical object associated with some defined subset of a resource that gives a lock holder the right to access the resource directly.