Tape Alert Log Page and the PC field

Kevin D Butt kdbutt at us.ibm.com
Tue Oct 29 07:44:34 PST 2002


* From the T10 Reflector (t10 at t10.org), posted by:
* "Kevin D Butt" <kdbutt at us.ibm.com>
*

Thank you for your responses.  As Pat points out, there is overriding text
in SSC that tells you to ignore the PC field for TapeAlert.  This answers
the question asked.  (You use the Information Exceptions mode page to leard
which Tapealert flags are supported.)

Thanks,

Kevin D. Butt
Fibre Channel & SCSI Architect
IBM Tape Microcode,
6TYA, 9000 S. Rita Rd., Tucson, AZ  85744
Tie-line 321; Office: 520-799-5280, Lab: 799-2869, Fax: 799-4138, Email:
kdbutt at us.ibm.com


                                                                                                                                 
                      "Pat LaVarre"                                                                                              
                      <LAVARRE at iomega.c        To:       <t10 at t10.org>                                                           
                      om>                      cc:                                                                               
                      Sent by:                 Subject:  RE: Tape Alert Log Page and the PC field                                
                      owner-t10 at t10.org                                                                                          
                                                                                                                                 
                                                                                                                                 
                      10/28/2002 03:31                                                                                           
                      PM                                                                                                         
                                                                                                                                 
                                                                                                                                 



* From the T10 Reflector (t10 at t10.org), posted by:
* "Pat LaVarre" <LAVARRE at iomega.com>
*
> A PC field of 10b is supposed to return the
> "default threshold values" of a log page.

I thought the "PC field" mentioned here by Kevin B was
not the so-called PC field of the data bytes[0] & xC0,
reserved in formal Scsi, but rather the PC field of
the Cdb[2] & xC0?

SPC mostly covers the PC of the Cdb, including the
quote "10 ... Indicates that the device server returns
default threshold values." but over in SSC we find the
quietly overriding text:

http://members.aol.com/plscsi/devices.html
ftp://ftp.t10.org/t10/drafts/spc2/spc2r20.pdf
ftp://ftp.t10.org/t10/drafts/ssc/ssc-r22.pdf

"5.2.11.2 TapeAlert log sense format
...
"The TapeAlert data is event based and the page
control bits in the LOG SENSE command are not
applicable and shall be ignored by the device. ...

Yes?

Curiously yours in breathtaking ignorance, Pat LaVarre

http://www.tuxedo.org/~esr/jargon/html/entry/language-lawyer.html
... A language lawyer is distinguished by the ability
to show you the five sentences scattered through a
200-plus-page manual that together imply the answer to
your question "if only you had thought to look there".
...

-----Original Message-----
From: Doug.C.Pirie at seagate.com [mailto:Doug.C.Pirie at seagate.com]
Sent: Mon 10/21/2002 1:52 PM
To: t10 at t10.org
Cc:
Subject: Tape Alert Log Page and the PC field

* From the T10 Reflector (t10 at t10.org), posted by:
* Doug.C.Pirie at seagate.com
*
I've seen applications that set byte 2 to a value of
0x2E and other applications that have set byte 2 to
0x6E and so on. I would suggest simply enabling your
firmware to ignore the PC bits for this page and then
just return your Tape Alert data. Since the TapeAlert
page does not really have the concept of thresholds
and the only flags of interest to an application are
the flags that are set I would say that it is to much
work for no gain to scratch your head trying to figure
out how to fit this page into a classic SCSI response.

Cheers,
Doug Pirie
Staff Applications Engineer
Seagate Removable Storage Solutions

-----Original Message-----
From: Dennis.W.Painter at seagate.com [mailto:Dennis.W.Painter at seagate.com]
Sent: Mon 10/21/2002 11:18 AM
To: kdbutt at us.ibm.com
Cc: owner-t10 at t10.org; t10 at t10.org
Subject: Re: Tape Alert Log Page and the PC field

* From the T10 Reflector (t10 at t10.org), posted by:
* Dennis.W.Painter at seagate.com
*
Hi Kevin,

For historical reasons what would be the PC field in
the TA log page is reserved.

I think what you are asking is "how can the client
determine what TA flags are supported"

You should be able to issue a mode select to page 1Ch
with the Test Flag Number set to 7FFFh (set all
supported flags). Then Log Select the TA page and the
flags set are the flags supported.

Hope this helps
Cheers
Dennis

-----Original Message-----
From: Kevin D Butt [mailto:kdbutt at us.ibm.com]
Sent: Fri 10/18/2002 5:08 PM
To: t10 at t10.org
Cc:
Subject: Tape Alert Log Page and the PC field

* From the T10 Reflector (t10 at t10.org), posted by:
* "Kevin D Butt" <kdbutt at us.ibm.com>
*
I have a question about how the PC field is used in
the industry in relation to the Tape Alert flags (log
page 0x2E).

A PC field of 10b is supposed to return the "default
threshold values" of a log page.

In the TapeAlert log page all 64 parameters are to be
returned regardless of whether or not they are
supported.

I have been informed that in the industry, application
clients use a  default threshold value of zero to
indicate that a parameter is not  supported.  Is this
true?

What is implied by the standards regarding the default
threshold value when a parameter is not supported.

Especially in the case of the Tape Alert page?

Thanks,
Kevin D. Butt
Fibre Channel & SCSI Architect
IBM Tape Microcode,
6TYA, 9000 S. Rita Rd., Tucson, AZ  85744
Tie-line 321; Office: 520-799-5280, Lab: 799-2869, Fax: 799-4138, Email:
kdbutt at us.ibm.com
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