2.4 UNIT ATTENTION Condition

The RESERVE, RELEASE, RESERVE EXTENDED, and RELEASE EXTENDED commands should be issued with the specification of ORDERED QUEUE. If any of these commands is issued with the specification of HEAD OF QUEUE, the command may cause the duplicated reserved status with a command that has been issued before.

Since the TEST UNIT READY and INQUIRY commands do not affect the HDD status, they can be issued with the specification of HEAD OF QUEUE.

An INIT can specify error recovery options with the QErr bits of the control mode parameter (Page A) of the Mode Select parameters. Deferred errors may be reported for commands whose processing has already ended. Therefore, the queue tag values assigned to those commands are not reported.

Use ABORT TASK, ABORT TASK SET, CLEAR TASK SET, or LOGICAL UNIT RESET to clear some or all of the queued commands.

2.4 UNIT ATTENTION Condition

The Unit Attention condition is a function for notifying the INIT asynchronously of events (status changes) which occur in the TARG or logical unit.

2.4.1 Generation of the UNIT ATTENTION condition

Events which cause the Unit Attention condition to be generated are any of the following events.

(1) When a Power On or RESET occurs

If the HDD is reset by a power on, HARD RESET, or LOGICAL UNIT RESET, regardless of whether the disk drive is in the ready state or not, the Unit Attention condition is generated to all the INITs.

(2) When I-T Nexus Loss occurs

When I-T Nexus Loss has been detected and command processing of an INIT that has detected the I-T Nexus Loss is aborted, the Unit Attention condition is generated for the INIT.

(3) When drive parameters are changed (if changed by another INIT)

If any of the following parameters is changed from an INIT, the Unit Attention condition is generated for all the INITs except the one that changes that parameter:

A parameter specified by the MODE SELECT or MODE SELECT EXTENDED command

A parameter specified by the SET DEVICE IDENTIFIER command

C141-C013

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Fujitsu MBC2036RC Unit Attention Condition, Generation of the Unit Attention condition, When a Power On or Reset occurs