The GRD is a central repository for locks and resources, it is distributed across all nodes (not a single node), but only one instance masters a resource. The process of maintaining information about resources is called lock mastering or resource mastering. I spoke about lock remastering in my BACKUP section.
Resource affinity allows the resource mastering of the frequently used resources on its local node, it uses dynamic resource mastering to move the location of the resource masters. Normally resource mastering only happens when an instance joins or leaves the RAC environment, as of Oracle 10g R2 mastering occurs at the object level which helps fine-grained object remastering. There are a number of parameters that can be used to dynamically remaster an object
_gc_affinity_time specifies interval minutes for re-mastering
_gc_affinity_limit defines the number of times a instance access the resource before remastering, setting to 0 disables remastering
_gc_affinity_minimum defines the minimum number of times a instance access the resource before remastering
_lm_file_affinity disables dynamic remastering for the objects belonging to those files
_lm_dynamic_remastering enable or disable remastering
You should consult Oracle before changing any of the above parameters.