Printing from ILE/C program running in QUSRWRK

Good morning, colleagues
It should be very simple, but looks like I am missing something
fundamental..

When I need to generate printed output from my C program, I write something
like:

....
FILE *LogFile ;
char szTemp[133] ;

LogFile = fopen("*LIBL/EQRPT", "w") ; // EQRPT - generic PRTF
sprintf(szTemp, "Printed output\n") ;
fwrite (szTemp, strlen(szTemp), 1, LogFile) ;
fclose(LogFile) ;

....

works fine in batch and interactive programs. Produces a spool file in an
output queue as expected.

However, when I place the same code in a program that runs in QUSRWRK (job
QZRCSRVS - a remote program call),
LogFile is *NULL after fopen and errno is 3025: "No such path or directory"
produces strerror.
I run the job under debugger using strsrvjob to check if EQRPT is indeed in
the path - I see that it is.

Can someone explain what am I doing wrong?

Thanks in advance,
Jevgeni.