Astonished by embedded sql

I don't understand the use of this embedded sql instead of using a CHAIN operation. Hopefully someone will explain.

A file is read by the RPG cycle (primary file) and the subroutine is called for every record of the file.
This file contains a couple of hundred thousand records.

It seems to me that this is the equivalent of opening myfile for each subroutine call, reading every record in the file then closing the file again.
Although I'm not sure about the reading. Is the whole file read at the open cursor statement?

Myfile has a couple of hundred records. For the whole primary file only about 10 different values for someDateField will be used.


D MyFile_DS E DS EXTNAME (myfile) QUALIFIED

Begsr mysr

wSql = 'Select * From myfile '+
'Where myfield = ''' + %Char(someDateField) + ''' ';

Exec SQL
Prepare S2 From :wSql;

If SqlCod < 0;
//Treat error
EndIf;

Exec SQL
Declare C2 Cursor For S2;

Exec SQL
Open C2;

If SqlCod < 0;
//Treat error
EndIf;

DoU SqlCod <> 0;
Exec SQL
Fetch Next from C2 Into :MyFile_DS;
Leave;

EndDo;

Exec SQL
Close C2;

EndSr;