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3.2 Look-Ahead Cache Feature
C141-C013 131
a) Data read by a READ or a READ EXTENDED command and which have
been read to the data buffer by Look-Ahead are data which are objects of
caching. Depending on the timing for halting Look-Ahead, it is possible that
data read by the READ command will be overwritten by Look-Ahead.
b) Data which have been hit by the READ or READ EXTENDED command
and transferred to the INIT once are also objects of caching as long as they
are not invalidated.
c) Data transferred from the INIT and written to the disk media by the WRITE
and WRITE EXTENDED, command are objects of caching.
d) Data transferred from the INIT and written to the disk media by WRITE
AND VERIFY command is not the objects of caching.
(3) Disabling caching data
Various data which are objects of caching in the data buffer are disabled in the
following cases.
a) If any of the following commands is issued for the same data block as data
which are the object of caching, that data block ceases to be an object of
caching.
− WRITE
− WRITE EXTENDED
− WRITE AND VERIFY
b) If any of the following commands is issued, all the data which are objects of
caching are disabled.
− LOG SELECT
− MODE SELECT
− MODE SENSE
− READ BUFFER
− READ DEFECT DATA
− READ LONG
− RECEIVE DIAGNOSTIC RESULTS
− SEND DIAGNOSTIC
− START/STOP UNIT
− WRITE LONG
− FORMAT UNIT
− LOG SENSE
− MODE SELECT EXTENDED