Nature of config_knobs

Are uvm_config_knobs extended from uvm_object transient or static in nature?

In reply to bl4ckp3rl :

Which uvm_config_knobs do you mean? I did not find a class withe this name in the UVM-Lib.

In reply to chr_sue:

Sorry for the confusion i meant control knob /configuration object such as agent configuration nature , are they static or transient ?
Thanks

In reply to bl4ckp3rl :
You are still mixing different things.
Control knobs are class members in a sequence definition. They are valid and existing as long as the sequence exists. A sequence is a transient object.
Configuration objects are classes which contain configuration data. If they are used in uvm_components they are existing as long as the simulation runs. If they are used in a sequence they exist as long as the sequence object exists.