X3T9.2/90-168 Rev 2

                                                    Date: 3/8/91


John Lohmeyer
Chairman X3T9.2

Subject:   SCSI   Function to allow User  Friendly  Long  Busy

     The  attached  revision  2 of the user  friendly  long  busy 
proposal  includes  the editorial changes noted in  the  February 
X3T9.2 plenary meeting. Consequently this is the version voted by 
the plenary for inclusion in SCSI-3.

     As  you know, this document includes only the additions  and 
changes  resulting from the proposal. For brevity, the  unchanged 
portions from SCSI-2 are not included in this document except for 
the Control Mode Page Table 7-66 itself.

     Please  let  me  know  if you have  any  questions  or  need 
anything further regarding its inclusion in SCSI-3.





                                   G.E. Milligan
                                   Director, Product Strategy



Additions and related changes to the Control Mode Page:

7.3.3.1. Control Mode Page

                        Table 7-66: Control Mode Page

==============================================================================
  Bit|   7    |   6    |   5    |   4    |   3    |   2    |   1    |   0    |
Byte |        |        |        |        |        |        |        |        |
==============================================================================
 0   |   PS   |Reserved|         Page Code (0Ah)                             |
-----|-----------------------------------------------------------------------|
 1   |                           Page Length (0Ah)                           |
-----|-----------------------------------------------------------------------|
 2   |                           Reserved                           |  RLEC  |
-----|-----------------------------------------------------------------------|
 3   |     Queue Algorithm Modifier      |Reserved|Reserved|  QErr  |  DQue  |
-----|-----------------------------------------------------------------------|
 4   |  EECA  |   RAC  |         Reserved         | RAENP  | UAAENP | EAENP  |
-----|-----------------------------------------------------------------------|
 5   |                           Reserved                                    |
-----|-----------------------------------------------------------------------|
 6   |                                                                       |
-----|---                        Ready AEN Holdoff Period                 ---|
 7   |                                                                       |
-----|-----------------------------------------------------------------------|
 8   |                                                                       |
-----|---                        Busy Timeout Period                      ---|
 9   |                                                                       |
-----|-----------------------------------------------------------------------|
 10  |                           Reserved                                    |
-----|-----------------------------------------------------------------------|
 11  |                           Reserved                                    |
==============================================================================

  The   Report  a  Check (RAC) bit provides control  of  reporting  long  busy 
conditions   or  CHECK  CONDITION status. A RAC bit of one  specifies  that  a  
CHECK CONDITION  status should  be reported rather than a long busy  condition  
(e.g.  longer  than  the Busy Timeout Period).  A RAC  bit of  zero  specifies  
that  long  busy conditions (e.g. busy condition during  extended  contingence 
allegiance) may be reported.

  The  Busy  Timeout  Period  field  specifies  the  maximum  time,  in    100 
milliseconds  increments, that the initiator allows for the target  to  remain 
busy  for  unanticipated conditions which are not a routine part  of  commands 
from  the  initiator. This value may be rounded down as defined  in  6.5.4.  A 
0000h  value  in this field is undefined by this standard. An FFFFh  value  in 
this field is defined as an unlimited period.

Change to Extended Contingent Allegiance Condition:


6.7. Extended Contingent Allegiance Condition

  "   ...  This condition shall be preserved until it is cleared  by   a  BUS   
DEVICE  RESET   message,   a  RELEASE RECOVERY message,  or  a    hard   reset    
condition.  While   the   extended  contingent   allegiance condition   exists  
the   target  shall    respond   to  any  other  request for   access  to  the   
logical    unit    from  another  initiator  with   BUSY  status  or  a  CHECK  
CONDITION   status  with  an appropriate sense  key  (e.g.  RECOVERED    ERROR   
(01h)  or ABORTED COMMAND (0Bh)) and a LOGICAL  UNIT   IS   IN   AN   EXTENDED  
CONTINGENT  ALLEGIANCE CONDITION additional sense code dependent upon the  RAC  
bit   in   the   Control  Mode  page.    ...  After  the  extended  contingent   
allegiance    condition    is  cleared any commands remaining in  the  command 
queue  shall   be executed."