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6.2 INIT Error Recovery Methods (Recommended)
C141-C013 373
(1) TASK SET FULL status
This status indicates that the HDD is currently executing processing of another
command and that a new command cannot be received. The INIT that receives
this status can reissue the original command.
Under a multi-initiator environment, when an INIT receives this status, the time
until the HDD can receive the next command depends on the operating state with
other INITs, so ordinarily, it cannot be predicted. In such a case, it is necessary
for the INIT that issued the command for which this status was received to
repeatedly issue the command until it is accepted.
(2) RESERVATION CONFLICT status
This status shows, under a multi-initiator environment, that the HDD is currently
reserved by another INIT, and cannot be used until that reserved status is released.
The period over which the reserved status continues should be managed by the
system, but normally, an INIT that receives this status reissues the original
command after waiting an appropriate length of time. The wait time until a
command is reissued is generally an inherent value of the system and it is
necessary that consideration be given to the operating states of the other INITs in
the system when deciding it.
Of the INIT which reserved the HDD falls into a state which it cannot recover
from for any reason before the reserved state is released, it will be impossible for
other INITs to access the HDD because that reserved state will continue. In such
a case, it is necessary for the INIT to take one of the following measures to
forcibly release the reserved state and recover the access right.
• HARD RESET sequence
(3) Command completion wait time-out
This error is a state where the completed status for a command is not reported
within the time expected by the INIT that issued the command.
One cause of this error occurring, besides a malfunction of the HDD, is that the
command was cleared by some method which the INIT that issued the command
cannot clearly detect, such as a HARD RESET sequence, or the command was
cleared when an unrecoverable error was detected in arbitration processing
executed by the HDD, etc. When this error occurs, then judge which recovery
method to use based on the contents of the sense data (see Section 6.2.2).
Not only does command execution time differ widely depending on the type and
specified contents of the command, but since it has an influence on the following
factors, it is necessary to give adequate consideration to these points when setting
the monitoring time value at the INIT.