Section: Configuration and Resource Classes

The configuration and resources classes provide access to a centralized
database where type specific information can be stored and received.
The <uvm_resource_db> is the low level resource database which users
can write to or read from. The <uvm_config_db> is layered on top
of the resoure database and provides a typed interface for configuration
setting that is consistent with the <uvm_component::Configuration Interface>.

Information can be read from or written to the database at any time during 
simulation. A resource may be associated with a specific
hierarchical scope of a <uvm_component> or it may be visible to all
components regardless of their hierarchical position.