SCSI Commands: 19BLOCATE
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42
3.7
LOCATE
The LOCATE command moves to a specified position on the tape.
Before the LOCATE operation is performed, all buffered data and filemarks are
transferred to tape. On completion, the logical position is before the specified
location.
3.7.1
LOCATE Command Descriptor Block
Byte
Bits
7 6 5 4 3 2 1 0
0
Operation Code (2Bh)
1
Ignored LUN
Reserved
IMMED
2
Reserved
3
(MSB)
4
5
6
Block Address
(LSB)
7
Reserved
8
Reserved
9
Control
3.7.1.1
LOCATE Command Field Descriptions
Field Bytes
Bits
Description
Operation
Code
0
The operation code for LOCATE is 2Bh
Ignored
Logical
Unit
1
5-7
The LUN field is vestigial from the SCSI-1 standard and is ignored.
IMMED
1
0
0 = Status is not returned until the tape is positioned.
1 = Status is returned as soon as the operation is initiated.
Block
Address
3-6
The logical block address of the block to which the tape is to be
positioned. Block 0 is the first block on tape. The value indicates the
total number of records and marks between BOM and the desired
logical position.
Reserved
All reserved bits must be 0.
Control 9
See
SCSI Command Control Byte Format on page 25.
The LOCATE command causes the logical position on tape to be set to the value
indicated by the Block Address field. The value indicates the total number of records
and marks between BOM and the desired logical position. A value of 0 will cause the
tape to be positioned at BOM.
If the immediate (IMMED) bit is set to one, then the drive validates the command
and waits for any previous command from any host to complete including any
immediate commands currently being processed and for any buffered data to be
flushed to tape. It will then report a deferred error for any preceding command or
buffered data if appropriate. If there is no deferred error, the drive reports good
status and initiates the command. If the immediate (IMMED) bit is set to zero, status
is not returned until after the command has completed.
Summary of Contents for LTO 4
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