User Guide

Ampex 1308911-02 B-21
Device Special Files Introduction
Table B-8. Device Special File Interface Parameter Description
Mnemonic
Name (Bit Location)
Description
DST_APPEND_ONLY
Append only
(Ox0000100)
On — Allows writing only at end of recorded data (EOD). Note that this is not the
same as the open call O_APPEND flag, which the tape device driver does not
support.
Off — Allows writing at any position up to and including EOD (even if it results
in overwriting of previously recorded data).
DST_DEF_POS_OPN
Set default position on
open (Ox0000400)
On — If the current position is undefined, a load command is issued on open to
set the current position to BOT. Otherwise, the current position is not changed
during open.
Off — The current position is not changed during open.
Note: When the DST_RETEN_OPN parameter is set to on, it overrides this
parameter.
DST_IGN_FM
Ignore filemark on first
read (Ox0008000))
On — If a filemark is encountered during the first read command after open and
no data was transferred, the filemark is ignored and the read command is
re-issued.
Off — If a filemark is encountered during the first read command after open and
no data was transferred, zero bytes are returned after encountering the filemark.
DST_NO_FM
No filemark written on
close (Ox0000002)
On — Filemark is not written to tape automatically on close. (You can, however,
write a filemark at or before close by issuing a Write Filemark command.
Off — When write is the last command issued before close, a single filemark is
written to tape at the end of recorded data. This action flushes the tape drive buffer
to tape.
DST_NO_FLUSH
No flush (Ox0000008)
On — During operation, any filemarks written to tape are buffered and the tape
drive buffer is not flushed to tape on close. One exception is that if a flush buffer
command is issued (i.e., write zero filemarks), the tape drive buffer is flushed to
tape regardless of this parameter value.
Off — Filemarks written to tape are unbuffered and the tape drive buffer is flushed
to tape on close.
Note: The DST_SYNC_WRITE parameter controls tape drive behavior when a
Write Data command is issued.
DST_NO_OPN_CMD
No commands issued on
open (Ox0000010)
On — Inhibits commands from being issued on open; i.e., overrides the default
settings for the device special file and forces the following interface parameters to
the states shown:
Parameter State
DST_NO_RESERVE On
DST_RETEN_OPN Off
DST_DEF_POS_OPN Off
DST_SBLK_SIZE Off
Off — Clears Unit Attention conditions and enables commands to be issued on
open; i.e., implements the default settings for the device special file.