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When commands with a HEAD OF QUEUE TAG are received continuously, the IDD executes
the latest command to be received first.
The RESERVE, RELEASE, RESERVE EXTENDED and RELEASE EXTENDED commands
should be issued together with an ORDERED QUEUE TAG. If HEAD OF QUEUE is used
with these commands, it may result in duplication of the previously issued command and the
Reserve state.
The TEST UNIT READY and INQUIRY commands do not exert an influence on the IDD's
state, so they can be issued together with a HEAD OF QUEUE TAG.
The INIT can specify two recovery options by the QErr bit of the control mode parameter
(Page A) of the Mode Select parameters, but this IDD does not support the QErr bit.
Reporting of commands for which deferred errors were previously terminated is done.
Therefore, the queue tag values assigned to those commands are not reported.
Use ABORT TASK SET, ABTS, TARGET RESET or CLEAR TASK SET to clear some or all
of the queued commands.
If "0001" is specified by the Queue algorithm modifier in the control mode page, the IDD
performs reordering processing of commands with respect to commands issued together with
the SIMPLE QUEUE TAG. Reordering processing is performed with the purpose of reducing
the total processing time in command processing.
• Conditions for Reordering:
If commands which are objects of reordering are issued by an INIT which permits
reordering together with a SIMPLE QUEUE TAG.
• Commands which are Objects of Reordering:
READ, READ EXTENDED, WRITE, WRITE EXTENDED
If the INIT permits command reordering processing, the IDD changes the command
processing order. It is necessary for the INIT to control concerning the validity of data.
For details of the control mode page, see 4.1.5, "MODE SELECT (15)".
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C141-E054-02EN
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