page 1 of 14


Date: March 8, 1988                                         X3T9.2/88-006R2

Revised: May 16, 1988

Revised: July 11, 1988

To: X3T9.2 Committee (SCSI)   

From: James McGrath (Quantum)

Subject: LOG SELECT and LOG SENSE commands




FIRST REVISION:

  This is the first revision of the LOG SELECT/SENSE proposal.  It
incorporates the input of the May working group session.  This
proposal does not cover the form of counters, or their content (this
is an issue Bill Spence will be addressing).


SECOND REVISION:

  This is the second revision of the LOG SELECT/SENSE proposal.  It
incorporates the input of the June plennary group session.
Specifically, more attention is paid to the issue of non-savable
parameters and the form of parameters (counters and lists).  The
architecture of the proposal does not differ from that of the first
revision.  Some additional clarifications, drawn from the MODE
SELECT/SENSE sections, in introduced.

  Note that old wording that has been dropped is enclosed in "[[",
"]]", while new wording that has been added is enclosed in "<<",
">>".




X.Y    LOG SELECT Command

     <<Peripheral Device Type:  All
        Operation Code Type:  See specific device type>>

                                                               page 2 of 14




         Table X.Y-1: LOG SELECT CDB

======================================================================
  Bit|   7   |   6   |   5   |   4   |   3   |   2   |   1   |   0   |
Byte |       |       |       |       |       |       |       |       |
======================================================================
 0   |                      Operation Code (TBD)                     |
-----|---------------------------------------------------------------|
 1   | Logical Unit Number   |        Reserved               |   SP  |
-----|---------------------------------------------------------------|
 2   |       PC        |    Reserved                                 |
-----|---------------------------------------------------------------|
 3   |                      Reserved                                 |
-----|---------------------------------------------------------------|
 4   |                      Reserved                                 |
-----|---------------------------------------------------------------|
 5   |                      Reserved                                 |
-----|---------------------------------------------------------------|
 6   |                      Reserved                                 |
-----|---------------------------------------------------------------|
 7   | (MSB)                                                         |
-----|---                   Parameter List Length                 ---|
 8   |                                                         (LSB) |
-----|---------------------------------------------------------------|
 9   |                      Control Byte                             |
======================================================================


  The LOG SELECT command provides a means for the initiator to manage
statistical information maintained by the device about the device or
attached logical units.  <<Targets that implement the LOG SELECT
command shall also implement the LOG SENSE command.  Initiators
should issue LOG SENSE prior to LOG SELECT to determine supported
pages, page lengths, and other parameters.>>

  <<If an initiator sends a LOG SELECT that changes any parameters
that apply to other initiators, the target shall generate a unit
attention condition for all initiators except the one that issued the
LOG SELECT command (see section 6.1.3).  The additional sense code
reported for the unit attention condition shall be LOG SELECT
PARAMETERS CHANGED.>>

  <<The target may provide for independent sets of parameters for
each attached logical unit or for each combination of logical unit
and initiator.>>

  <<If the initiator sends a value for a parameter that is outside
the range supported by the target and rounding is not implemented for
that parameter, the target shall terminate the command with CHECK
CONDITION status, the sense key set to ILLEGAL REQUEST, and the
additional sense code set to INVALID FIELD IN PARAMETER LIST.>>

                                                               page 3 of 14




X.Y.1    CDB Fields

  [[A save parameters (SP) bit of zero indicates the target shall
perform the specified LOG SELECT operation, and may or may not save
any parameters.  A SP bit of one indicates that the target shall
perform the specified LOG SELECT operation, and shall save all
savable parameters to a non-volatile vendor specific location
including any sent during the DATA OUT phase.]]

  <<A save pages (SP) bit of zero indicates the target shall perform
the specified LOG SELECT operation, and may or may not save any
parameters.  A SP bit of one indicates that the target shall perform
the specified LOG SELECT operation, and shall save to a non-volatile
vendor specific location all the savable parameters including any
sent during the DATA OUT phase.>>

  <<The target is expected to save, at vendor specific times, the
savable parameters to a non-volatile vendor specific location.  This
implicit saving operation shall be done frequently enough to insure
that the parameter values retain statistical significance across
power cycles.>>

  <<Savable parameters are optional and identified by the DS bit that
is returned in the parameter control byte by the LOG SENSE command.
If the target does not implement saved parameters and the SP bit is
set to one, the command shall be terminated with CHECK CONDITION
status, the sense key shall be set to ILLEGAL REQUEST, with an
additional sense code of ILLEGAL FIELD IN COMMAND DESCRIPTOR BLOCK.>>

  The page control (PC) field defines the type of parameter values to
be selected.  The page control field is defined in Table X.Y-2.  See
section X.Y.2 for an explanation of the types of parameter values.


       Table X.Y-2: Page Control Field

======================================================================
                Bit 7  Bit 6  Type of Parameter Values 
                -----  -----  ------------------------ 
                  0      0    Threshold Values         
                  0      1    Cumulative Values        
                  1      0    Reserved
                  1      1    Reserved
======================================================================


  <<The parameter list length field specifies the length in bytes of
the LOG SELECT parameter list that shall be transferred from the
initiator to the target during the DATA OUT phase.  A parameter list
length of zero indicates that no data shall be transferred.  This
condition shall not be considered as an error.>>

                                                               page 4 of 14




  If multiple pages are sent during this DATA OUT phase then they
shall be sent in ascending order according to page code.  If multiple
parameters within a page are sent during this DATA OUT phase then
they shall be sent in ascending order according to parameter code.  

  A parameter list length that results in the truncation of any page
header or parameter shall cause the target to terminate the command
with CHECK CONDITION status.  The sense key shall be set to ILLEGAL
REQUEST, and the additional sense code shall be set to INVALID FIELD
IN COMMAND DESCRIPTOR BLOCK. 


X.Y.2    Type of Parameter Values

  The LOG SELECT command supports two types of parameter values for
each log parameter.  The cumulative value is updated by the
target to reflect the cumulative record of events experienced by the
target.  It may also be updated by the initiator via the LOG SELECT
command.

  IMPLEMENTOR'S NOTE:  updating the cumulative parameters via the LOG
  SELECT command may be used to reset the parameter value to a
  default state (e.g. zero).  The default cumulative value, read by
  the initiator using the LOG SENSE command, provides the default
  values suggested by the target manufacturer.

  The updating and saving of cumulative parameters may be controlled
by bits set in the parameter control byte (see section X.Y-5).

  The threshold value can only be modified by the initiator via the
LOG SELECT command.  When cumulative values are updated, they are
compared to the threshold values.  When the threshold has been met,
the target shall indicate this by posting to all initiators an UNIT
ATTENTION condition, with the additional sense code set to THRESHOLD
CONDITION MET.  Those targets that support the AEN protocol may use
it instead of posting an UNIT ATTENTION condition.

  If the <<initiator attempts to change>> threshold values are not
available or not implemented for the parameter the LOG SELECT command
shall be terminated with CHECK CONDITION status with the sense key
set to ILLEGAL REQUEST and the additional sense code set to THRESHOLD
PARAMETERS NOT SUPPORTED.

  The saving of threshold parameters and the criteria for the
threshold being met may be controlled by bits set in the parameter
control byte (see section X.Y-5).


X.Y.3    Page Structure

  The format of the LOG SELECT/SENSE data consists of zero or more
variable-length pages.  Each page starts with a 4-byte page header
followed by one or more variable-length parameters associated with
that page.  The 4-byte header is illustrated in <<Table>>[[Figure]]
X.Y-3.
                                                               page 5 of 14




    Table X.Y-3: SELECT LOG Page Structure

======================================================================
  Bit|   7   |   6   |   5   |   4   |   3   |   2   |   1   |   0   |
Byte |       |       |       |       |       |       |       |       |
======================================================================
 0   |                      <<PAGE Code (__h)>>[[Reserved]]          |
-----|---------------------------------------------------------------|
 1   |                      <<Reserved>>[[PAGE Code (__h)]]          |
-----|---------------------------------------------------------------|
 2   | (MSB)                                                         |
-----|---                   Page Length (n)                       ---|
 3   |                                                         (LSB) |
-----|---------------------------------------------------------------|
 4   |                                                               |
- - -|- -                   Page-Specific Parameters              - -|
n + 3|                                                               |
======================================================================


  The page code field identifies which page of data is being
transferred.  If the page code value is reserved or not implemented
by the target, then the target shall terminate the command with a
CHECK CONDITION status.  The sense key shall be set to ILLEGAL
REQUEST, and the additional sense code shall be set to INVALID FIELD
IN PARAMETER LIST.

  The page parameter length field defines the length, in bytes, of
the page-specific parameters.  This length does not include bytes
zero through three.  A page parameter length value that results in
the truncation of any [[or]] parameter shall cause the target to
terminate the command with CHECK CONDITION status.  The sense key
shall be set to ILLEGAL REQUEST, and the additional sense code shall
be set to INVALID FIELD IN COMMAND DESCRIPTOR BLOCK. 

  The page-specific parameters are defined within the appropriate
page definitions <<in section _____>>.


X.Y.4    Parameter Structure

  The format of the LOG SELECT/SENSE pages consists of zero or more
variable-length parameters.  Each parameter starts with a 4-byte
parameter header followed by one or more bytes of parameter value for
that parameter.  The 4-byte header is illustrated in <<Table>>
[[Figure]] X.Y-4.


                                                               page 6 of 14



       Table X.Y-4: SELECT LOG Parameter Structure

======================================================================
  Bit|   7   |   6   |   5   |   4   |   3   |   2   |   1   |   0   |
Byte |       |       |       |       |       |       |       |       |
======================================================================
 0   | (MSB)                                                         |
-----|---                   Parameter Code (p)                    ---|
 1   |                                                         (LSB) |
-----|---------------------------------------------------------------|
 2   |                      Parameter Control Byte                   |
-----|---------------------------------------------------------------|
 3   |                      Parameter Length (n)                     |
-----|---------------------------------------------------------------|
 4   |                                                               |
- - -|- -                   Parameter Value Bytes                 - -|
n + 3|                                                               |
======================================================================


  The parameter code field identifies which parameter of data is
being transferred.  If the parameter code value is reserved or not
implemented by the target, then the target shall terminate the
command with a CHECK CONDITION status.  The sense key shall be set to
ILLEGAL REQUEST, and the additional sense code shall be set to
INVALID FIELD IN PARAMETER LIST.

  The parameter control byte contains bits and fields that control
how the target and initiator use the parameter.  See section X.Y.5
for an explanation of these fields.

  The parameter length field defines the length, in bytes, of the
parameter value.  This length does not include bytes zero through
three.  A parameter length value that results in the truncation of
the parameter shall cause the target to terminate the command with
CHECK CONDITION status.  The sense key shall be set to ILLEGAL
REQUEST, and the additional sense code shall be set to INVALID FIELD
IN PARAMETER LIST.

  <<If the initiator sends a value for a parameter that is outside
the range supported by the target and rounding is implemented for
that parameter, the target may either:>>

  <<(1) round the value to an acceptable value and terminate the
command as described in section 6._._.>>

  <<(2) terminate the command with CHECK CONDITION status, the sense
key set to ILLEGAL REQUEST, and the additional sense code set to
Invalid Field In Parameter List.>>

  The meaning of the parameter values are defined within the
appropriate parameter definitions <<in section ____>>.


                                                               page 7 of 14




X.Y.5    Parameter Control Byte

  The parameter control byte is part of the parameter header, and
controls the manner in which the cumulative parameter values are
updated, saved, and compared to the threshold parameter values.  It
also indicates the type of parameter (e.g. counter).


      Table X.Y-5: SELECT LOG Parameter Control Byte

======================================================================
  Bit|   7   |   6   |   5   |   4   |   3   |   2   |   1   |   0   |
======================================================================
     |   DU  |   DS  |   ET  |   Operation   |Reserved|      FP      |
======================================================================


  A disable update (DU) bit of zero indicates that the target shall
update the cumulative parameter value to reflect all of the events
that should be noted by that parameter.  This update operation may
use volatile memory, and thus the value is not guaranteed to survive
a power cycle.

  A DU bit of one indicates that the target shall not update the
cumulative parameter value except in response to a LOG SELECT
command.

  The DU bit is ignored for the threshold parameter value.

  [[A disable save (DS) bit of zero indicates that the target shall
save, at vendor specific times, the cumulative or threshold parameter
value to a non-volatile vendor specific location.  This implicit
saving operation shall be done frequently enough to insure that the
cumulative parameter values retain statistical significance across
power cycles.]]

  <<A disable save (DS) bit of zero indicates that the target shall
save the cumulative or threshold parameter value to a non-volatile
vendor specific location in response to a LOG SELECT command with the
SP bit set.  The target may also save cumulative or threshold
parameter value at vendor specific times.  This implicit saving
operation shall be done frequently enough to insure that the
cumulative parameter values retain statistical significance across
power cycles.>>

  [[A DS bit of one indicates that the target shall only save the
cumulative or threshold parameter value to a non-volatile vendor
specific location in response to a LOG SELECT command with the SP bit
set.]]

  <<A DS bit of one indicates that the target shall not save the
cumulative or threshold parameter value to a non-volatile vendor
specific location under any circumstances, and specifically in
response to a LOG SELECT command with the SP bit set.>>

                                                               page 8 of 14




  An enable threshold (ET) bit of zero indicates that the cumulative
parameter value is never compared to the threshold parameter value.

  An ET bit of one indicates that when the cumulative parameter value
is updated, it is compared to the threshold parameter value.

  Setting the ET <<bit>> to a certain <<value>>[[option]] for either
the cumulative or threshold parameter [[value]] forces the target to
set the ET bit of the other parameter [[value]] to that same
<<value>>[[option]].

  The operation field is a control variable.  It defines the binary
relationship between the cumulative and threshold parameter values
under which the threshold is met.  When the threshold is met, then a
UNIT ATTENTION condition shall be posted to all initiators, with an
additional sense code THRESHOLD CONDITION MET.  <<Note that the value
of the parameter control byte as well as the parameter byte values
may be compared.>> {Still unresolved in how to terminate the
condition met status, since resetting the parameter value on read to
its default value both violates the concept of a cumulative value and
does not work well in a multiple initiator environment.}


     Table X.Y-6: Threshold Met Criteria

======================================================================
                Bit 4  Bit 3  Threshold Met Criteria   
                -----  -----  ------------------------ 
                  0      0    any update of parameter
                  0      1    cumulative = threshold
                [[1      0    cumulative > threshold]]
                <<1      0    cumulative <> threshold>>
                  1      1    cumulative >= threshold
======================================================================


  Setting the operation field to a certain criteria for either the
cumulative or threshold parameter [[value]] forces the target to set
the operation field of the other parameter [[value]] to that same
criteria.

  The form of parameter (FP) bit shall be ignored.

                                                               page 9 of 14




X.Z    LOG SENSE Command

     <<Peripheral Device Type:  All
        Operation Code Type:  See specific device type>>


          Table X.Z-1: LOG SENSE CDB

======================================================================
  Bit|   7   |   6   |   5   |   4   |   3   |   2   |   1   |   0   |
Byte |       |       |       |       |       |       |       |       |
======================================================================
 0   |                      Operation Code (TBD)                     |
-----|---------------------------------------------------------------|
 1   | Logical Unit Number   |    Reserved                   |   SP  |
-----|---------------------------------------------------------------|
 2   |        PC       |    Page Code (__h)                          |
-----|---------------------------------------------------------------|
 3   |                      Reserved                                 |
-----|---------------------------------------------------------------|
 4   |                      Reserved                                 |
-----|---------------------------------------------------------------|
 5   |                      Reserved                                 |
-----|---------------------------------------------------------------|
 6   |                      Reserved                                 |
-----|---------------------------------------------------------------|
 7   | (MSB)                                                         |
-----|---                   Allocation Length                     ---|
 8   |                                                         (LSB) |
-----|---------------------------------------------------------------|
 9   |                      Control Byte                             |
======================================================================


  The LOG SENSE command provides a means for the initiator to
retrieve statistical information maintained by the device about the
device or attached logical units.  It is a complementary command to
the LOG SELECT command.


X.Z.1    CDB Fields

  [[A save parameters (SP) bit of zero indicates the target shall
perform the specified LOG SENSE operation, and may or may not save
any parameters.  A SP bit of one indicates that the target shall
perform the specified LOG SENSE operation, and shall save all savable
parameters to a non-volatile vendor specific location.]]

  [[The target is expected to save, at vendor specific times, the
savable parameters to this non-volatile vendor specific location.
This implicit saving operation shall be done frequently enough to
insure that the parameter values retain statistical significance
across power cycles.]]

                                                               page 10 of 14




  <<A save pages (SP) bit of zero indicates the target shall perform
the specified LOG SENSE operation, and may or may not save any
parameters.  A SP bit of one indicates that the target shall perform
the specified LOG SENSE operation, and shall save to a non-volatile
vendor specific location all the savable parameters including any
sent during the DATA OUT phase.>>

  <<The target is expected to save, at vendor specific times, the
savable parameters to a non-volatile vendor specific location.  This
implicit saving operation shall be done frequently enough to insure
that the parameter values retain statistical significance across
power cycles.>>

  <<Savable parameters are optional and identified by the DS bit that
is returned in the parameter control byte by the LOG SENSE command.
If the target does not implement saved parameters and the SP bit is
set to one, the command shall be terminated with CHECK CONDITION
status, the sense key shall be set to ILLEGAL REQUEST, with an
additional sense code of ILLEGAL FIELD IN COMMAND DESCRIPTOR BLOCK.>>

  The page control (PC) field defines the type of parameter values to
be selected.  The page control field is defined in Table X.Z-2.


       Table X.Z-2: Page Control Field

======================================================================
                Bit 7  Bit 6  Type of Parameter Values
                -----  -----  ------------------------
                  0      0    Threshold Values        
                  0      1    Cumulative Values       
                  1      0    Default Threshold Values
                  1      1    Default Cumulative Values
======================================================================


  The allocation length field specifies the number of bytes that the
initiator has allocated for returned LOG SENSE data.  An allocation
length of zero indicates that no LOG SENSE data shall be transferred.
This condition shall not be considered as an error.  Any other value
indicates the maximum number of bytes that shall be transferred.  The
target shall terminate the DATA IN phase when allocation length bytes
have been transferred or when all available LOG SENSE data have been
transferred to the initiator, whichever is less.

  <<If multiple pages are transferred during this DATA IN phase then
they shall be transferred in ascending order according to page code.
If multiple parameters within a page are transferred during this DATA
IN phase then they shall be transferred in ascending order according
to parameter code.>>

  <<If the target does not support a parameter code within this page
then it shall not return and data associated with the parameter for
any of the page code values.>>

                                                               page 11 of 14




X.Z.2    Type of Parameter Values

  The LOG SENSE command supports four types of parameter values for
each log parameter.  The cumulative and threshold parameter values
are the same as those defined for the LOG SELECT command (see section
X.Y.2).  Note that the cumulative parameter values returned are:

  1) The values since the last update (done by either the target or
     in response to a LOG SELECT or LOG SENSE command).

  2) The saved values if an update has not occurred since the last
     power-on RESET condition and saved parameters are implemented.

  3) The default values if an update has not occurred since the last
     power-on RESET condition and saved parameters values are not
     available or not implemented.

  The threshold parameter values returned are:

  1) The values since the last update via a successful LOG SELECT
     command.

  2) The saved values if an update has not occurred since the last
     power-on RESET condition and saved parameters are implemented.

  3) The default values if an update has not occurred since the last
     power-on RESET condition and saved parameters values are not
     available or not implemented.


  The default cumulative parameter values are provided to the
initiator by the target so that the cumulative parameters may be
reset to a default condition by a LOG SELECT command after executing
a LOG SENSE command.  The default threshold parameter values are
provided to the initiator by the target so that the threshold
parameters may be reset to a vendor specific condition by a LOG
SELECT command after executing a LOG SENSE command.

  IMPLEMENTOR'S NOTE: this vendor specific condition usually
  indicates a reasonable level at which a threshold met condition
  should be detected, and the initiator notified to do a LOG SENSE.
  For example, if the parameter tracks an error rate, then the
  default value for this parameter might be the specified rate, or
  the specified rate plus some variance.


X.Z.3    Page Structure

  The page structure is the same as that defined for the LOG SELECT
command (see section X.Y.3).

                                                               page 12 of 14




X.Z.4    Parameter Structure

  The parameter structure is the same as that defined for the LOG
SELECT command (see section X.Y.4).


X.Z.5    Parameter Control Byte

  The parameter control byte is the same as that defined for the LOG
SELECT command (see section X.Y.5) for the cumulative and threshold
parameter values.  

  For the default cumulative and threshold parameter values, the
value of the DU bit indicates the target's default updating option of
the cumulative parameter values.

  For the default cumulative and threshold parameter values, a DS bit
of zero indicates that the saving of the corresponding parameter
value is implemented by the target, while a bit of one indicates that
the saving of the corresponding parameter value is not implemented by
the target.

  For the default cumulative and threshold parameter values, an ET
bit of zero indicates that the threshold function is not supported
for this parameter, while a bit of one indicates that the threshold
function is supported for this parameter.  The same value of the ET
bit is returned for both the default cumulative and default threshold
parameter values.

  For the default cumulative and threshold parameter values, the
operation field indicates the target's default threshold condition
met criteria.  The same criteria is returned for both the default
cumulative and default threshold parameter values.

  A form of parameter (FP) bit of zero indicates that the parameter
is a counter.  A FP bit of one indicates that the parameter is a list
of non-counter values.  The same value of the FP bit is returned for
all parameter types.


<<X.Z.6    Form of Parameter>>

<<X.Z.6.1    Data Counters>>

  <<A parameter may take the form of a data counter.  Parameters are
associated with one of more events.  Parameters are updated whenever
oen of these events occurs by the incrementation of the counter.
Each counter has associated with it a target defined maximum value.
Upon reaching this maximum value, the counter no longer increments
(does not wrap), but rather retains the maximum value and the DU bit
for the parameter is set to one, indicating that the counter has
overflowed.>>

                                                               page 13 of 14




<<X.Z.6.2    List Parameters>>

  <<A parameter may take the form of a list of bytes containing data
in a non-counter form.  The bytes shall be limited to printable ASCII
characters {more precise wording?}.  The meaning of the data reported
may be different for each parameter.>>

  <<If two list parameters are defined on a single page, then the
parameter updated last shall have a higher parameter code than that
updated first.  Only one exception is allowed, in which case the
parameter with the lower parameter code shall have been updated later
than any of the other list parameters on this page.>>

  <<IMPLEMENTOR'S NOTE: list parameters can be used to store the
  locations of defective sectors in the following manner.  When a
  defective sector is identified a list parameter is updated to
  reflect the location and cause of the defect.  When the next defect
  is encountered, the list parameter with the next parameter code
  value is used to record this defect.  This process continues until
  the parameter with the last parameter code defined for this page
  has been updated, in which case the next parameter updated to
  record a defective sector shall be the list parameter with the
  lowest parameter code on the page.  The process then continues as
  before.  The size of the page can be made target specific to
  accomodate memory limitations.  It is recommedned that one or more
  data counter parameters be defined for the page to keep track of
  the number of list parameters and the parameter code of the
  parameter with the oldest recorded defect. This technique can be
  adapted to record other types of information.>>

  <<{There is a problem here in that two LOG SENSE commands are
required to read the page - the first for the data counter values to
determine the number of list parameters, the second for the list
parameters.  In addition, all the list parameters must be read if the
one with the highest parameter code is desired.  The first problem
can be partially solved by including a bit in the CDB to disable the
sending of supported parameter values that have never been updated
from the default state.  The second can be solved by defining a new
two byte parameter in the CDB indicating the starting parameter
code value for the data transfer.}>>


<<X.Z.7    Summary List of Supported LOG SELECT/SENSE Pages>>


  <<The summary list of supported LOG SELECT/SENSE pages returns the
list of page codes supported by the target.  This page is defined in
table X.Z-3.>>

                                                               page 14 of 14




  <<Table X.Z-3: Summary List of Supported ACCESS LOG Pages>>
<<
======================================================================
  Bit|   7   |   6   |   5   |   4   |   3   |   2   |   1   |   0   |
Byte |       |       |       |       |       |       |       |       |
======================================================================
 0   |   Reserved    |        Page Code (00h)                        |
-----|---------------------------------------------------------------|
 1   |                        Reserved                               |
-----|---------------------------------------------------------------|
 2   | (MSB)                                                         |
-----|---                     Page Parameter Length               ---|
 3   |                                                         (LSB) |
-----|---------------------------------------------------------------|
 4   |                        First supported page number            |
- - -|- -                                                         - -|
n + 4|                        Last supported page number             |
======================================================================
>>

  <<This page returns the summary list of supported ACCESS LOG pages
for the logical unit to the Initiator.  If any other pages are
supported by the device, then support of page zero is mandatory.>>

  <<IMPLEMENTORS NOTE:  Typically, an initiator should first request
  page zero to determine the list of other supported pages within the
  device.>>

  <<The supported page number list begins at byte 4 and contains a
list, in ascending order, of the supported pages for the logical
unit.>>

  <<{This page may want to appear in another section.}>>