understanding inz in PI

hello,
Below is part of my code. In my procedure1 call, I am passing empty xmlDS. Is it required to define xmlDS with inz keyword in parameter section (d xmlDS         likeds(ds_xml) dim(3) inz) since its empty initially ? Can I use inz keyword in procedure interface or should be I using in the caller procedure of Myprocedure ? which one have less complications? Upon successful completion of Myprocedure1 xmlDS will have data and I am making a call to Myprocedure2 with empty DSfile1,DSfile2,DSfile3,DSfile4. So same question for DSFile1, DSFile2,DSFile3 and DSFile4? 
 
 
p Myprocedure b export
d procedure pi N
 
d fparm1   10 0
d fparm2   2a
d fparm3   22 0
d xmlDS         likeds(ds_xml) dim(333)
d DSfile1       likeds(file1ds)
d DSfile2       likeds(file2ds)
d DSfile3       likeds(file3ds)
d DSfile4       likeds(file4ds)
d DSerror        likeds(error_DS)
 
/free
 
if Myprocedure1(fparm1:fparm2:fparm3:   
                     :xmlDS:DSerror);
 
if Myprocedure2(fparm1:fparm2:fparm3:   
                    :xmlDS:DSFile1:DFile2:DSFile3:DSFile4:DSerror);
 
 
                      
 endif;
 
endif;
 
  
 
/end-free                             
 
 Thanks,
 
A