How to get config object from config db to the tb_top

UVM
,
5

In reply to chr_sue:
I did the following:

   // tx_fe forces and assignments
   assign tx_vif.cyc_tic = dut.tx_fe.cyc_tic_internal;
   initial begin
      start_of_simulation_ph.wait_for_state(UVM_PHASE_STARTED);      
      if(!uvm_config_db #(tx_agent_config)::get(null, "uvm_test_top.env",  "db_tx_agent_config", m_tx_cfg)) begin
      `uvm_error("top", "tx_agent_config not found")
	end//if
      if (m_tx_cfg.is_active == UVM_ACTIVE) begin 	 
	 force dut.tx_fe.xi_n = tx_vif.xi;
	 force dut.tx_fe.xq_n = tx_vif.xq;
      end
   end
   
 
   // rx_fe forces and assignments
   assign rx_vif.chind2 = dut.rx_fe.chind2;
   initial begin
      start_of_simulation_ph.wait_for_state(UVM_PHASE_STARTED);      
      if(!uvm_config_db #(rx_agent_config)::get(null, "uvm_test_top.env",  "db_rx_agent_config", m_rx_cfg)) begin
      `uvm_error("top", "rx_agent_config not found")
	end//if  
      if (m_rx_cfg.is_active == UVM_ACTIVE) begin  	 
	 force dut.rx_fe.x = rx_vif.x;
      end
   end

I got error when I try to run this:
UVM_ERROR …/sv/girobo2_tb_top.sv(175) @ 0: reporter [top] rx_agent_config not found