In reply to smukerji:
OK, I understand. It Looks like you do not understand the mechanism of the uvm_config_db. You do not store variables there. You store simple values of certain types. The value is assiciated with a name. The Name consists of the path and a simple Name (string). In your case the simple name is ‘error_source’. And the path is the concatenation of ‘this’ and an empty string. Where you have the question marks you have to use a local variable where the value will be stored in.