Kevin,

There are some ways that an action requested in a command may be deferred. Those are:

1) when the command supports the IMMED bit (MODE SENSE and MODE SELECT do not)

2) if the command has explicit rules defined as to when a specific action is to take place ( Mode parameter block descriptor in the mode page parameters is an example of that)

3) if a specific page has explicit rules defined as to when a specific value is to take affect. (I know of none but I did not do an extensive search)

If the mode parameters you are referring to in your note do not have explicit rules stating that are not required to take effect until a POR occurs then SAM requires them to be valid on completion of the MODE SELECT command. In other words there is nothing special about the MODE SELECT command that allows an implementation to treat mode pages any different that any other kind of parameter data.

Bye for now,
George Penokie

LSI Corporation
3033 41st St. NW
Suite 100
Rochester, MN 55901

507-328-9017
george.penokie@lsi.com

From: owner-t10@t10.org [mailto:owner-t10@t10.org] On Behalf Of Kevin D Butt
Sent: Wednesday, August 06, 2008 2:09 PM
To: t10@t10.org
Subject: Mode Parameter changes and when they take effect

I have a question related to Mode Parameters. I have searched SPC-4 (and earlier SPC versions) and cannot find guidance about when the changes to mode parameters take effect. This concern is related to configuration settings and differences in expectations of various vendors.

Vendor 1 claims that any change to a mode parameter shall become effective immediately and should not cause a device to reboot.
Vendor 2 claims that changes to some mode parameters require a reboot before they can be accomplished. As such the device automatically performs a POR on completion of the Mode Select that changes one or more of these parameters.
Vendor 3 also claims that changes to some mode parameters require a reboot before they can be accomplished. This device,however, requires that an outside entity send a command to force the device to perform a POR. The new values of the mode parameters are not in effect until after the POR.

In another form of when do parameters take effect, the requested change to the format (or density) does not occur until a subsequent command (e.g., a Format, a Write from BOT, etc.).

Is there any guidance in SPC?

Thanks,

Kevin D. Butt
SCSI & Fibre Channel Architect, Tape Firmware
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-2869 / 520-799-5280
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt@us.ibm.com
http://www-03.ibm.com/servers/storage/