HP C737990900 - Manual (Page 133)

Commands 133
Co
m
m
an
ds
■
Power On, SCSI Reset, Bus Device Reset
■
Media inserted
■
A load command executed by a third party
■
Mode Sense parameters changed by another initiator
■
Drive firmware has been updated
U NIT ATTENTION sense will persist for a host until the host sends a command
that has Unit Attention as part of its pre-execution checks. When the Unit
Attention pre-execution check fails, the UNIT ATTENTION sense is copied to the
Current sense and CHECK CONDITION status is reported to the host. The UNIT
ATTENTION sense is cleared. The host is then expected to issue a REQUEST
SENSE command to recover the UNIT ATTENTION sense (which is now the new
Current sense).
It is possible for multiple
UNIT ATTENTION conditions to arise (for example,
after a power-on followed by a tape load), such that the initiator does not read
one condition before the next occurs. In this case a prioritizing scheme is used.
If a UNIT ATTENTION condition exists and a new one occurs, then the UNIT
ATTENTION sense will be overwritten by the new sense only if the new sense
has a higher priority.
The order of priority is as follows:
U NIT ATTENTION sense that arises as a result of a command executing will not
be posted to the sending initiator, but will be set for the other initiators.
DEFERRED ERROR Sense
D EFERRED ERROR sense is generated when an operation fails and CHECK
CONDITION status cannot be reported to the host for one of the following
reasons:
■
The operation had immediate-report on (for example, REWIND with the
Immed bit set, or LOAD ).
■
The operation was a write that was immediate-reported on after its data
was successfully placed in the write-behind queue.
Power-on, Reset
Tape Loaded
Mode Parameters Changed
Microcode Downloaded
highest priority
lowest priority