In reply to skumarsamal:
When using the uvm_config_db, remember that the UVM paths of the set and get must match. In UVM, even if you’re inside a VMM hierarchy, the paths start at ‘uvm_test_top’ and go down from there. So, if your agent is inside a dummy component, its path will be ‘uvm_test_top.dummy.apb_master_agent’. If your
uvm_config_db#(virtual apb_master_if)::set(this, "apb_master_agent", "mst_if", top_tb.u0_T_wrapper.u0_apb_master_if);
call is done from this dummy component, then the path you are using on the set() call is {this.get_full_name(),“apb_master_agent”}. If your set() call is not done from the agent’s immediate parent, the paths won’t match. Try turning on +UVM_CONFIG_DB_TRACE