Save data pointers, Restore pointers, Disconnect – Dell PowerVault TL2000 User Manual
Page 102: Initiator detected error, Abort, Message reject, Save, Data, Pointers, Restore
The
Wide
Data
Transfer
Request
message
is
used
to
negotiate
the
width
of
the
data
path
for
the
data
transfers
between
the
media
changer
and
the
initiator.
The
width
applies
to
data
phases
only.
The
media
changer
does
not
support
wide
data
transfers.
When
it
receives
a
WDTR
message
from
the
initiator,
it
returns
a
WDTR
message
with
a
transfer
width
exponent
of
0
(8-bit
transfer
width).
The
successful
exchange
of
WDTR
message
implies
an
agreement
to
an
8-bit
data
transfer
width.
Bit
7
6
5
4
3
2
1
0
Byte
0
Extended
Message
(01h)
1
Extended
Message
Length
(02h)
2
Extended
Message
Code
(03h)
3
Transfer
Width
Exponent
The
Transfer
Width
field
determines
the
width
of
the
data
path
for
data
transfers.
The
media
changer
will
return
00h
for
this
field.
This
indicates
that
the
media
changer
supports
an
8-bit
data
transfer
width
only.
Save
Data
Pointers
The
SAVE
DATA
POINTERS
message
is
issued
before
every
disconnect
message
following
a
data
in
or
data
out
phase.
The
message
is
not
sent
when
disconnecting
after
a
command
descriptor
block
that
did
not
transfer
data.
Restore
Pointers
The
media
changer
sends
the
RESTORE
POINTERS
message
to
direct
the
initiator
to
copy
the
most
recently
saved
command,
data
and
status
pointers
of
the
I/0
process
to
the
corresponding
active
pointers.
The
command
and
status
pointers
are
restored
to
the
value
at
the
beginning
of
the
data
area.
The
media
changer
sends
the
Restore
Pointers
message
after
a
detecting
a
parity
error
during
the
command
phase
or
data
out
phase.
After
the
media
changer
successfully
sends
the
Restore
Pointers
message
to
the
initiator,
the
media
changer
restarts
the
command,
data
in,
data
out,
or
status
phase
from
the
beginning.
Disconnect
The
DISCONNECT
message
is
sent
by
a
target
to
inform
an
initiator
that
the
present
data
transfer
will
be
suspended.
the
target
will
reselect
the
initiator
at
a
later
time
to
continue
the
current
operation.
Initiator
Detected
Error
The
INITIATOR
DETECTED
ERROR
message
is
sent
from
an
initiator
to
inform
a
target
that
an
error
occurred.
This
allows
the
target
to
retry
the
operation.
Abort
The
ABORT
message
terminates
the
current
I/O
process.
The
target
goes
directly
to
the
BUS
FREE
phase
after
receipt
of
this
message.
Message
Reject
The
MESSAGE
REJECT
message
is
sent
from
the
initiator
or
target
to
indicate
that
the
last
message
received
was
inappropriate
or
not
implemented.
4-2
TL2000
and
TL4000
SCSI
Reference