HP Surestore 80fx Optical Drive and Library SCSI-2 Command Reference - Page 31

Table 1-5 SCSI Command Overview Drive Control Commands Clear Queue 0EH The drive goes to the BUS FREE phase following successful receipt of the CLEAR QUEUE message. The drive clears all I/O processes, from all initiators, in the queue for the specified logical unit from the queue. All active I/O processes are terminated. The medium may have been altered by partially executed commands. All pending status and data for that logical unit for all initiators are cleared. A unit attention condition is generated for all other initiators with I/O processes that either were active or were queued for that logical unit. The additional sense code is set to Command Cleared by Another Initiator. Queue Tag Messages (20H, 21H, 22H) The drive supports SIMPLE QUEUE TAG, HEAD OF QUEUE TAG, and ORDERED QUEUE TAG. The Queue Tag Messages consist of two consecutive bytes, Message Code (20H, 21H, or 22H) and Queue Tag (00H-FFH) to distinguish each I/O process. The Queue Tag of each I/O process must be unique for each I/O process, but the numeric value of a queue tag has no effect on the order of execution. Simple Queue Tag Byte 7 6 5 4 3 2 1 0 0 Message Code (20H) 1 Queue Tag (00H-FFH) The Simple Queue Tag message specifies that the I/O process be placed in the logical units command queue. The order of the execution may be altered within the constraints of the queue management algorithm specified in the control mode page. 1-12 Chapter 1