Depending on the value specified by the ACTION (or READONLY) specifier in the OPEN statement, the file will be opened by your program for reading, writing, or both reading and writing records. This simply checks that the program itself executes the type of statements intended.
For performance reasons, record locking and shared-file checking are not supported by Intel Fortran. When you open the file, access is always granted, regardless of whether:
The OPEN statement SHARED specifier was specified
Other processes have already opened the file
You might open a file for writing records (or reading and writing records) and know another process might simultaneously have the file open and be writing records. In this case, you need to coordinate access times among those processes to handle the possibility of simultaneous WRITE and REWRITE statements on the same record positions.