The READONLY specifier indicates only READ statements can refer to this connection. It takes the following form:
READONLY is similar to specifying ACTION='READ', but READONLY prevents deletion of the file if it is closed with STATUS='DELETE' in effect.
The Fortran I/O system's default privileges for file access are READWRITE. If access is denied, the I/O system automatically retries accessing the file for READ access.
However, if you use the compiler option specifying OpenVMS defaults, the I/O system does not retry accessing for READ access. So, run-time I/O errors can occur if the file protection does not permit WRITE access. To prevent such errors, if you wish to read a file for which you do not have write access, specify READONLY.