C141-E039-01EN
2 - 11
2.3
Write Cache
The IDD is equipped with a Write cache function in order to reduce the INIT's command
processing time. If that operation is permitted by the MODE SELECT command (caching
parameters: Page code = 8, WCE bit), at the point when the IDD completes the transfer of all
data specified in the WRITE or WRITE EXTENDED command, it reports the GOOD
statement and terminates the command.
Note:
If the Write cache function is permitted, data transferred form the INIT by a WRITE or
WRITE EXTENDED command are written to the disk media after the GOOD status is
reported, so when an unrecoverable write error is detected in that write operation, sense
data are generated. When those sense data are being held, the IDD ordinarily responds to
the command that is executed next by a "CHECK" status (deferred error), notifying the
INIT that sense data are being held. However, ordinarily, it is troublesome for the INIT to
retry when there is an unrecoverable error in a Write cache operation, so adequate caution
should be exercised when using this function.
