SUMMARY Command Tag Queuing

From: Luis Vallejo (
Date: Thu Mar 16 1995 - 01:22:57 CST

Sorry for the delay, this is so far some of the responses :

I'm running 2.3 and 2.4 also I have 4.1.3U1

Note: What kind of test can I run so I can see the difference between enable and disable command tag queuing?


In which OS?? 0x200 (from memory) in scsi_options

                l & h,

It's enabled in Solaris 2.x. Not supported in 1.x.
Can give you some nasty crashes with some drives that don't agree with Sun
on the implementation....


You don't say what OS version. Its on by default for Solaris 2.3 and
2.4, and maybe others.

For Solaris 2.3 (and 2.4, and maybe others), modify the /etc/system
file, scsi_options parameter. Note that this parameter is not noramally
contained in the file; you have to include it to use it.

Attached below is one of Sun's documents, available from SunSolve.

Hope this helps.


--- Begin document ---
SRDB ID: 10254

SYNOPSIS: enable disable scsi options


On the same system, same scsi bus 1 can find large scsi disk drives as well
as smaller ones. Recently, the large ones started supporting the 16 bit, or
wide scsi communication, while the smaller 1s can't. This situation leads
to prblems where the widescs i option should be disabled. Other differences
in scsi options implementations exist between drives , e.g., tagged queuing.
Following are the option bytes where there's 1 bit per option. bit=1 =>option
enabled, bit =0 option disabled.

Note: 0x means in hexade cimal

SCSI option value to set the corresponding bit to 1
Disconnect/reconnect 0x008 (bit3=1, starting with bit 0)
Linked commands 0x010 (bit4=1)
Synchronous transfer 0x020 (bit5=1)
Parity 0x040 (bit6=1)
Tagged Queuing 0x080 (bit7=1)
Fast scsi 0x100 (bit8=1, or bit 9 if starting with 1)
Wide scsi 0x200 (bit9=1)



To set a given set of options, one should add all the bit values corresponding
to those options , then include the result in a set statment in /etc/system.


1-To check the current options settings, as root does:

        #adb -k /kernel/unix /dev/mem
        #$q (to exit adb)
here's what my system gave:
nouiouat# adb -k /kernel/unix /dev/mem
physmem 1f0d
scsi_options: 178

0x178 means bits 3,4,5,6, and 8 are set to 1 hence, disc/reconnect, linked
commands, synchronous transfer, parity, and fast scsi are enabled.
Tagged Queuing and Wide scsi are set to 0, i.e., disabled.

2-To enable Wide SCSI add the following line in /etc/system:

        set scsi_options=0x3f8

3-to verify that the cahnge took effect,try the adb sequence given in 1.
  It should show 3f8.

PRODUCT: Gen. Admin
SUNOS RELEASE: Solaris 2.3

--- End document ---

Ralph Waters                | Internet:
Harris ISD, MS W2-7746      | Phone: (407) 984-5693
PO Box 98000                | FAX:   (407) 984-6323
Melbourne, Florida 3290


In Solaris 2.3 and 2.4 it is enabled by default.

regards, -- Glenn Satchell | There's a fine line Uniq Professional Services Pty Ltd ACN 056 279 335 | between fishing and PO Box 70, Paddington, NSW 2021, (Sydney) Australia | standing on the shore Phone 02 380 6360 Pager 016 287 000 Fax 02 380 6416 | looking like an idiot.

Thanks for the answers

Luis Vallejo Product Support Engineer Client Server/Systems Division EMC Corporation (508)435-1000 X 56315

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