Opening and closing the character device
Only one user can open the character device at any one time. Once you have opened the device, you must close it to make it accessible to other users.
About this task
The open function can fail (return a negative value)
with one of the following values for errno:
- EBUSY
- The device has already been opened by another user.
- EIO
- No IUCV connection to the z/VM MONITOR system service could be established. An error message with an IPUSER SEVER code is printed into syslog. See z/VM: Performance, SC24-6301 for details about the codes.
Once the device is opened, incoming messages are accepted and account for the message limit. If you keep the device open indefinitely, expect to eventually reach the message limit (with error code EOVERFLOW).