System response under SunOS 5.0 through 5.8 provides no bounds to the timing of I/O events. This means that synchronous I/O calls should never be included in any program segment whose execution is time critical. Even program segments that permit very large time bounds must not perform synchronous I/O. Mass storage I/O is such a case, where causing a read or write operation hangs the system while the operation takes place.
A common application mistake is to perform I/O to get error message text from disk. This should be done from an independent nonreal-time process or thread.