Hold bit and UA response.

Paul.A.Suhler at certance.com Paul.A.Suhler at certance.com
Wed May 18 17:25:39 PDT 2005


* From the T10 Reflector (t10 at t10.org), posted by:
* Paul.A.Suhler at certance.com
*

Hi, Kevin.

Well, the premise was that the Hold bit was set to one in the LOAD UNLOAD
CDB, so the application client should have know that if the command
finished without error then the MAM would be accessible.  Possible
combinations that could work:

1.  Non-immediate unload:  When GOOD status comes back, the MAM is
accessible.  A Unit Attention on the next command is superfluous.

2.  Immediate unload:  Application client can poll with TEST  UNIT READYs.
When it sees NOT READY / MEDIUM NOT PRESENT - MAM ACCESSIBLE (3A04h), it's
there.  Still superfluous.

Are people doing this now?

If no one is relying on the UA, then I guess that I wouldn't object to
changing it from notifying all to notifying all others.  Is there a
pressing need to make the change?

Thanks,

Paul
+++++++++++
Paul Suhler
Firmware Engineer
Quantum Corporation
1650 Sunflower Avenue
Costa Mesa, California  92626



                                                                                                                                       
                      "Kevin D Butt"                                                                                                   
                      <kdbutt at us.ibm.co        To:       "Kevin D Butt" <kdbutt at us.ibm.com>                                            
                      m>                       cc:       owner-t10 at t10.org, Paul.A.Suhler at certance.com, t10 at t10.org                    
                      Sent by:                 Subject:  Re: Hold bit and UA response.                                                 
                      owner-t10 at t10.org                                                                                                
                                                                                                                                       
                                                                                                                                       
                      05/18/2005 03:43                                                                                                 
                      PM                                                                                                               
                                                                                                                                       
                                                                                                                                       



Paul,

Perhaps the UA is needed because there is no other way for the target to
tell the application client that MAM is accessible even though it is Not
Ready.

Kevin D. Butt
Fibre Channel & SCSI Architect, IBM Tape Firmware,
6TYA, 9000 S. Rita Rd., Tucson, AZ  85744
Tie-line 321; Office: 520-799-5280, Lab: 799-5751, Fax: 799-4138, Email:
kdbutt at us.ibm.com

                                                                           
 Kevin D Butt/Tucson/IBM at IBMUS                                             
 Sent by: owner-t10 at t10.org                                                
                                                                           
                                                                        To 
 05/17/2005 02:55 PM                             Paul.A.Suhler at certance.co 
                                                 m                         
                                                                        cc 
                                                 owner-t10 at t10.org,        
                                                 t10 at t10.org               
                                                                   Subject 
                                                 Re: Hold bit and UA       
                                                 response.                 
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           


If we are to believe what we have been hearing lately, a lot of
applications don't even see the UA's as the device drivers swallow them.  I
don't know, but it seems abnormal for a UA to be returned to the I_T Nexus
that caused it by a command.

Thanks,

Kevin D. Butt
Fibre Channel & SCSI Architect, IBM Tape Firmware,
6TYA, 9000 S. Rita Rd., Tucson, AZ  85744
Tie-line 321; Office: 520-799-5280, Lab: 799-5751, Fax: 799-4138, Email:
kdbutt at us.ibm.com
                                                                           
 Paul.A.Suhler at certance.com                                                
                                                                           
                                                                           
 05/17/2005 02:26 PM                                                    To 
                                              Kevin D                      
                                              Butt/Tucson/IBM at IBMUS        
                                                                        cc 
                                              owner-t10 at t10.org,           
                                              t10 at t10.org                  
                                                                   Subject 
                                              Re: Hold bit and UA          
                                              response.                    
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           


Hi, Kevin.

I don't recall any discussion on the point when this first went into SSC.
I'm unable to construct a scenario where the application client that issued
the command needs the unit attention.  (I can see that it would be useful
if the HOLD bit were not set and IMMED was.  Then the application client
could poll until it sees the UA, then start talking to the MAM before
threading, etc. is finished.  *If* the device actually allowed that, which
isn't a given.)

The issue is now whether there would be any application clients that would
be broken by *not* getting the UA, were the change to be made.

Thanks,

Paul
++++++++++++++

                    "Kevin D Butt"

                    <kdbutt at us.ibm.co        To:       t10 at t10.org

                    m>                       cc:

                    Sent by:                 Subject:  Hold bit and UA
response.
                    owner-t10 at t10.org



                    05/17/2005 12:03

                    PM


In SSC-3r01c under the Load/Unload command, Clause 7.2 pg 76 there is this
description of the HOLD bit.

A LOAD bit of one and a HOLD bit of one specifies if the medium has not
been moved into the logical unit, the
medium shall be moved in but not positioned for access. The EOT and RETEN
bits shall be set to zero. Following
successful completion, the device server shall return GOOD status. If both
the medium and device server support
MAM, the device server shall generate a unit attention condition for all
initiators and the additional sense code shall
be set to MEDIUM AUXILIARY MEMORY ACCESSIBLE.

My question is if the intent is that the UA be generated for "all
initiators" as is stated, or if the intent is to generate the UA for "all
other I_T Nexuses"?

Thanks,

Kevin D. Butt
Fibre Channel & SCSI Architect, IBM Tape Firmware,
6TYA, 9000 S. Rita Rd., Tucson, AZ  85744
Tie-line 321; Office: 520-799-5280, Lab: 799-5751, Fax: 799-4138, Email:
kdbutt at us.ibm.com




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