The READONLY specifier indicates only READ statements can refer to this connection. It takes the following form:
READONLY
READONLY is similar to specifying ACTION='READ', but READONLY prevents deletion of the file if it is closed with STATUS='DELETE' in effect.
Default file access privileges are READWRITE, which can cause run-time I/O errors if the file protection does not permit write access.
The READONLY specifier has no effect on the protection specified for a file. Its main purpose is to allow a file to be read simultaneously by two or more programs. For example, use READONLY if you wish to open a file so you can read it, but you also want others to be able to read the same file while you have it open.
For details on file sharing, see your user manual.