sqlrpgle host variable definition confusion

Hello,



I often get the message SQL0312 ( not defined or not usable) when trying to
use cursors and local variables in a sub procedure. I'm guessing that it's
a problem of the precompiler, maybe there's some rules to avoid this
problem?

But here is a case I just had which I don't understand :


In the example below, when the data structure is declared with « likerec »,
the compiler returns two messages (SQL0312) saying that SD and MyField “are
not defined or not usable”.


If I use the “extname” definition, there are no errors. But in this case,
the data structure isn’t qualified, so why does it compile?



Why does the first not compile and why does the second compile with no
error?

d*SD ds likerec ( DSPF_Record : *ALL )

d SD e ds extname ( MyDspF : DSPF_Record )



exec sql

declare c1 cursor for

select *from myTable where : SD.MyField <> '';



Thanks