Having problems accessing IFS from RPGIV

I am having 2 problems access the IFS system from an RPGIV program.   Any
help would be greatly appreciated.  We are running v4r2.

1)  I am having a weird problem with my open() function.  It will work fine
the day I compile the program but the next day it will fail.  If I recompile
the program without making any source changes it will again for that day.
On both days I am trying to open the same text file.  The text file has not
be altered in any way.   The open is for ready only.

2) I am trying to retrieve the value of errno when a function fails without
success.  Here is a snippet of my code.   The variable errno always contains
0 even when the FileHandle is -1.

D errnoF          PR              *   EXTPROC('__errno')

D errnoP          S               *                 
D errno           S             10I 0 BASED(errnoP)

C                   Eval      FileHandle=open(%addr(FilePath):oflag)
C                   EVAL      errnoP = errnoF                       
C     'errno'       DSPLY                   errno         


Thanks for you help


Mark           
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