Global Configuration Values (GCVs) are settings that are similar to driver parameters. GCVs are constant values, not global variables. There is no way to change a GCV value at runtime. the GCVs are globally accessible to the driver and driver set, but not to the tree or network.
Given these facts, GCVs are constants and cannot be changed at runtime, but they can be consumed by all drivers in a driver set or by all policies in a driver. This makes GCVs a very powerful configuration tool. The following guidelines are used when developing driver configuration files with GCVs.