The IOSTAT keyword specifies I/O status. It takes the following form:
IOSTAT = ios
This keyword causes ios to be defined as follows:
IOSTAT applies only to the OPEN statement in which it appears and not to subsequent I/O operations on the logical unit that is opened. However, you can use the IOSTAT keyword in subsequent I/O statements to perform a similar function.
Secondary operating system messages do not display when IOSTAT is specified. To display these messages, remove IOSTAT or use a platform-specific method such as an OpenVMS condition handler.