MPLIR05552I File not open on non-optional.

The file was not successfully opened.

See the CTF tracing for a more through understanding of why this may have occurred. (File doesn't exist on disk, etc. ) Will typically have a 9/0xx trace indicating the COBOL RTS System Error Code that describes the reason for failing to open.

Resolution:
Correct the environment or logic error that caused the issue. PL/I RTS #fileio ctf tracing may provide you with additional information as to the root cause.
Module:
cp1op.c, mf1io.pl1