Stored procedure on apex 18 working perfect
Simple checking availability of free roms/houses/cars... any other assets from bigest oracle databases should be realised with simple stored procedures (not working with apex 4.2.6 dont know why ? but working with apex 2.2/5.1/5.2/18)

https://apex.oracle.com/pls/apex/f?p=26341

its recreated stored procedures from google,  p_enter_plandate i was renamed and
changed if conditions and variables, for testing it on oracle apex 5.2

create or replace procedure "CHS"
( datum1 IN DATE,
  min1 IN NUMBER default 90,
  message OUT varchar2 )
is
countt number :=0;
cursor checking (datum1 in date, min1 in number) is
select count(*) from bkcc_pro pro
where datum1 = sysdate;
begin
      open checking (datum1, min1);
      fetch checking into countt;
      if (countt = 0) then
          insert into bkcc_pro (pro_id, pro_begin, pro_minutee, pro_available, pro_bocked)
        values (bkcc_pro_seq.nextval, datum1, min1, 0, 0);
       message := 'One record successfull inserted';
     elsif (countt = 1) then
       message := 'no record ';
     else
     message := 'next duplicate record ';
     end if;
     close checking;
end;

Oracle apex 18 found all procedures and show it on popup, but apex 4.2.6 cant found and when I put in search field forms are not created

Anyway, stored procedures works good on apex 5/18

apex 4.2 demo all diagrams