User Guide

6-50 Ampex 1308911-02
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dd2_setpos_tape DD-2 Utilities Manual Pages
The -position <position_spec> argument comprises a multi-element specification ordered as
described below. Each element must be delineated by colons and included in the specification
even if left empty (a space between colons is not considered empty).
To specify a DD-2 position, provide a six-element -position <position_spec> ordered as
follows: -position :postype:volid:adfn:ptid:fsn:ldbn:. Valid parameters for the elements are
listed below.
postype Must contain the literal string DD2, signifying that the position is in
DD-2 form.
volid The volume ID written to the VFI area on the tape. This is an arbitrary
6-byte value. Each byte can be any value, except all 6 bytes cannot be
binary zero. You can specify the volume ID in one of two ways:
• You can supply six or fewer printable ASCII characters. If you
supply fewer than six characters, the command left-justifies your
input string and pads the right part of the volume ID with ASCII
spaces.
• You can supply a 12-digit hexadecimal number prefixed by 0x. This
number can be any value that is not all zeroes. The command does
not pad your input; you must supply all 12 digits.
The volume ID is used to verify that the correct tape is mounted. If the
volume ID on the tape does not match the one supplied, this command
fails. You can leave this element empty, in which case the command uses
the currently-mounted tape without checking the volume ID.
adfn Absolute Double Frame Number - The number of the physical block
that contains the specified location. This is an optional value that,
strictly speaking, is not part of the position specification. When used, it
provides a very accurate hint to the drive, expediting high-speed
positioning to the specified position.
LEAVE THIS ELEMENT EMPTY IF YOU ARE NOT SURE OF THE
ADFN! A BAD ADFN CAN LEAVE THE POSITION AT AN
INVALID TAPE LOCATION (SUCH AS PAST EOD).
ptid Partition Identification Number (ID) - The number of the partition that
contains the specified location. Partitions are numbered sequentially on
the tape, starting at zero.
Leave this element empty to specify the current partition.
fsn The number of the file section that contains the specified location. Files
are numbered sequentially within a partition, starting at one.