When the application cannot handle a critical error that occurs, critical-error handling can be reset to the system. This is done by having DosSetFHState turn off the fail/errors bit and then reissuing the I/O function. The expected critical error recurs, and control is passed to the system critical-error handler. The precise time that the effect of this function is visible at the application level is unpredictable when asynchronous I/O operations are pending.

The Direct Open bit parameter is the "Direct I/O flag." It provides an access mechanism to a disk or diskette volume independent of the file system. This mode should be used only by system programs and not by application programs.

Named-Pipe Considerations

As defined by the operating system, D = 0. Other bits are as defined by DosCreateNPipe (serving end), DosOpen (client end), or the last DosSetFHState.