Sun Microsystems, Inc.   Sun System Handbook - ISO 3.4 June 2011 Internal/Partner Edition
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SCSI Option Bit

SCSI Option Bit Setting

Use the following procedure to determine the SCSI option bit setting under Solaris 2.x:

# adb -k /kernel/unix /dev/mem (Solaris 2.0 - 2.4)
# adb -k /dev/ksyms /dev/mem (Solaris 2.5)
scsi_options/X
$q

SCSI Option Bits

Disconnect/Reconnect 0x008
Linked Commands 0x010
Synchronous Transfer 0x020
Parity 0x040
Tagged Queuing 0x080
Fast SCSI 0x100
Wide SCSI 0x200
Fast 20 0x400

Tagged Queuing

Tagged Queuing allows a disk to receive more than one command at a time and to perform the commands in an order that reduces disk latency in many applications. Tagged Queuing is implemented in Solaris 2.1.

Some SCSI disk drives may not properly implement Tagged Queuing. Disable Tagged Queuing in the driver to prevent unrecoverable failures. Add the following to the /etc/system file under Solaris 2.x:

set scsi_options=0x178

Wide SCSI

To enable Wide SCSI under Solaris 2.3, add the following to the /etc/system file:

set scsi_options=0x3f8


Last updated: December 2, 1996
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