X3T9.2/90-168

                                                Date: 10/30/90

John Lohmeyer
Chairman X3T9.2

Subject:   SCSI   Function to allow User  Friendly  Long  Busy

     As a result of the discussions of my earlier proposal for 
an  Automatic Reservation on Check (ARC) it became clear  that 
the root problem was due to long busy conditions. While  their 
was strong disagreement on ARC, there was general agreement on 
the benefit of accommodating many operating systems which give 
up on long busy conditions.

     I  accepted  an action item from the 30  October  working 
group  meeting  to add a Report Busy/Report Check bit  in  the 
control mode page.

     As  is  my custom, the proposal does  not  duplicate  the 
paragraphs  which  are not changed. It only provides  the  new 
paragraphs.

     The attachment fulfills the action item.




                                   G.E. Milligan
                                   Director, Product Strategy



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 (06h)                           |
-----|-----------------------------------------------------------------------|
 2   |                           Reserved                           |  RLEC  |
-----|-----------------------------------------------------------------------|
 3   |     Queue Algorithm Modifier      |Resserv.|Resserv.|  QErr  |  DQue  |
-----|-----------------------------------------------------------------------|
 4   |  EECA  |   RAC  |       Reserved           | RAENP  | UAAENP | EAENP  |
-----|-----------------------------------------------------------------------|
 5   |                           Reserved                                    |
-----|-----------------------------------------------------------------------|
 6   |                                                                       |
-----|---                        Ready AEN Holdoff Period                 ---|
 7   |                                                                       |
==============================================================================


  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  500 milliseconds). A RAC bit of zero specifies  that  long  busy 
conditions (e.g. busy condition during extended contingence allegiance) may be 
reported.


  In addition, make the following change:


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  a 
RECOVERED  ERROR  sense  key  (01h) and an 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."