lr_advance_param("param1"); - it is a loadrunner function which helps in advancing the parameter value to the next row in the table.
How does it helps :
When the scenario is like if we have a parameter variable at various places in the script,But we need to pass the
parameter value with advancement only at certian places. In such a case, we can't provide update on each iteration as it passes same value across each iteration.Also, We can't provide update on each occurence as it passes different values for each occurence.
So in such a case lr_advance_param("param1") functions help much better in the places wherever the parameter expects the
update.