SCSI command

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In SCSI computer storage, a command is the basic unit of communication. The SCSI command architecture was originally defined for parallel SCSI buses but has been carried forward with minimal change for use with Fibre Channel, iSCSI and Serial Attached SCSI.

In SCSI protocol, the initiator sends a SCSI command to the target which then responds. SCSI commands are sent in a Command Descriptor Block (CDB). The CDB consists of a one byte operation code followed by five or more bytes containing command-specific parameters. At the end of the command the target returns a Status Code byte.

The rest of this article contains a list of SCSI commands, firstly in operation code order and secondly in alphabetical order. There are links to detailed descriptions for the more common SCSI commands:

[edit] List of SCSI commands by operation code

Code	Command
00	TEST UNIT READY
01	REZERO UNIT
03	REQUEST SENSE
04	FORMAT UNIT
07	REASSIGN BLOCKS
08	READ (6)
0A	WRITE (6)
0B	SEEK (6)
11	SPACE (6)
12	INQUIRY
15	MODE SELECT (6)
16	RESERVE (6)
17	RELEASE (6)
18	COPY
1A	MODE SENSE (6)
1B	START/STOP UNIT
1C	RECEIVE DIAGNOSTIC RESULTS
1D	SEND DIAGNOSTIC
1E	PREVENT/ALLOW MEDIUM REMOVAL
23	READ FORMAT CAPACITIES (MMC)
25	READ CAPACITY
28	READ (10)
2A	WRITE (10)
2B	SEEK (10)
2E	WRITE AND VERIFY
2F	VERIFY
30	SEARCH DATA HIGH
31	SEARCH DATA EQUAL
32	SEARCH DATA LOW
33	SET LIMITS (10)
34	PRE-FETCH
35	SYNCHRONIZE CACHE
36	LOCK/UNLOCK CACHE
37	READ DEFECT DATA
39	COMPARE
3A	COPY AND VERIFY
3B	WRITE BUFFER
3C	READ BUFFER
3E	READ LONG
3F	WRITE LONG
40	CHANGE DEFINITION
41	WRITE SAME
4C	LOG SELECT
4D	LOG SENSE
50	XDWRITE
51	XPWRITE
52	XDREAD
55	MODE SELECT (10)
56	RESERVE (10)
57	RELEASE (10)
5A	MODE SENSE (10)
5E	PERSISTENT RESERVE IN
5F	PERSISTENT RESERVE OUT
80	XDWRITE EXTENDED
82	REGENERATE
A0	REPORT LUNS
A5	MOVE MEDIUM
A8	READ (12)
AA	WRITE (12)
B3	SET LIMITS (12)
B4	READ ELEMENT STATUS
B7	READ DEFECT DATA (12)

[edit] List of SCSI commands, alphabetical

Code	Command
40	CHANGE DEFINITION
39	COMPARE
18	COPY
3A	COPY AND VERIFY
04	FORMAT UNIT
12	INQUIRY {Mandatory}
36	LOCK/UNLOCK CACHE
4C	LOG SELECT
4D	LOG SENSE
15	MODE SELECT (6)
55	MODE SELECT (10)
1A	MODE SENSE (6)
5A	MODE SENSE (10)
A5	MOVE MEDIUM
5E	PERSISTENT RESERVE IN
5F	PERSISTENT RESERVE OUT
34	PRE-FETCH
1E	PREVENT/ALLOW MEDIUM REMOVAL
08	READ (6)
28	READ (10)
A8	READ (12)
3C	READ BUFFER
25	READ CAPACITY
37	READ DEFECT DATA (10)
B7	READ DEFECT DATA (12)
B4	READ ELEMENT STATUS
23	READ FORMAT CAPACITIES (MMC)
3E	READ LONG
07	REASSIGN BLOCKS
1C	RECEIVE DIAGNOSTIC RESULTS
82	REGENERATE
17	RELEASE (6)
57	RELEASE (10)
A0	REPORT LUNS
03	REQUEST SENSE {Mandatory}
16	RESERVE (6)
56	RESERVE (10)
01	REZERO UNIT
31	SEARCH DATA EQUAL
30	SEARCH DATA HIGH
32	SEARCH DATA LOW
0B	SEEK (6)
2B	SEEK (10)
1D	SEND DIAGNOSTIC {Mandatory}
33	SET LIMITS (10)
B3	SET LIMITS (12)
11	SPACE (6)
1B	START/STOP UNIT
35	SYNCHRONIZE CACHE
00	TEST UNIT READY {Mandatory}
2F	VERIFY
0A	WRITE (6)
2A	WRITE (10)
AA	WRITE (12)
2E	WRITE AND VERIFY
3B	WRITE BUFFER
3F	WRITE LONG
41	WRITE SAME
52	XDREAD
50	XDWRITE
80	XDWRITE EXTENDED
51	XPWRITE