IBM IC35L036UWDY10 Hard Drive Specifications - Page 221

! Commands which cause an OVERLAPPED COMMANDS ATTEMPTED error. See Section 11.1.3 , "Incorrect Initiator Connection" on page 194. 11.3.1 Queue depth Any initiator can queue at least one command at any time irrespective of the actions of any other initiators in the system. A single initiator may queue up to 128 commands, if no other initiator has more than one command in the queue, although at times this maximum may be reduced as the drive can reserve command blocks for internal use. 11.3.2 Tagged queuing Commands with a tag message are saved in the command queue. Queued commands will be reordered by the drive defined rule. See Section 11.4, "Command reordering" on page 206 for details. 11.3.3 Untagged queuing The drive supports queuing one I/O process from each initiator. If the drive receives an untagged I/O process while executing an I/O process from a different initiator, the untagged I/O process may be queued. The drive treats untagged I/O processes as though they were received with Simple Queue Tag messages for purposes of queuing. 11.3.4 Command queuing rule Commands can be received during an active I/O process if the Bus is free. I/O processes of READ(6), READ EXTEND(10), WRITE(6) and WRITE EXTEND(10) can be active at the same time. See Section 11.5 , "Concurrent I/O Process" on page 206 for details. 11.3.5 QUEUE FULL status This status is returned when a SIMPLE, ORDERED, or HEAD OF QUEUE tag message is received and the command queue is full. The I/O process is not placed in the command queue. Since one queue element is reserved for each initiator, any untagged command that does not cause Incorrect Initiator Connection will not cause QUEUE FULL status. 11.3.6 Device behavior on Command queuing 1. Initiators must send a Queue tag immediately after the IDENTIFY message in MESSAGE OUT phase just after SELECTION. Targets send a SIMPLE queue tag immediately after the Identify message in MESSAGE IN phase just after RESELECTION. 2. Each initiator can issue either a tagged command or an untagged command exclusively at the same time. Other initiators can exist which operate mutually exclusively with tagged or untagged commands. 3. When DQue (Mode Page A) is set to1, if an initiator issues a tagged command, the drive returns MESSAGE REJECT message (07h) and receives that command as an untagged command. 4. Queue Tag number does not affect the order of execution. 5. If an initiator issues a command with a queue tag which is the same as the current I/O process or queued I/O process, the drive may return Incorrect Initiator connection. See Section 11.1.3 , "Incorrect Initiator Connection" on page 194. 6. A series of linked commands are a single I/O process and are assigned the queue tag established in the initial selection. A command received with a HEAD OF QUEUE tag message shall not suspend a series of linked commands for which the drive has begun execution. 7. If DQue is changed to 1 while queued commands exist, all queued commands for the all initiators will be aborted. All future commands received from any initiator with a queue tag will be processed Ultrastar 146Z10 hard disk drive specifications 205