In order to add debug messages to APEX pages you can use the following syntax :
wwv_flow.debug('This is my debug message');wwv_flow.debug('### The value of P1_TEST_ITEM is ' || :P1_TEST_ITEM);You can even include HTML tags to make your debug messages stand out from the Oracle debug text :
wwv_flow.debug('<font color="red">P1_TEST_ITEM = ' || :P1_TEST_ITEM || '</font>');