User's Guide

Commands: Space (11h) Page 155
Command Descriptor Block Field Descriptions
The following table provides descriptions of the CDB fields.
Field
Name Bytes Bits Description
Code 1 0-2 The Code Field designates the desired function as shown below:
Bits
2 1 0 Function
0 0 0 Space blocks
0 0 1 Space filemarks
0 1 0 Space sequential filemarks
0 1 1 Space to end of recorded data
1 0 0 Space setmarks
Count 2-4 This field specifies the number of blocks, filemarks, sequential filemarks, or
setmarks to space over. A zero value in the Count field causes no media
movement and is not considered an error.
Space-by-Count Functions
The Count field indicates both direction and distance within the current partition. A
positive value N in the Count field moves the tape forward over N blocks, filemarks,
contiguous filemarks, or setmarks. A negative value -N (2's complement) in the
Count field moves the tape backward over N blocks, filemarks, or setmarks. Zero in
the count field causes no tape movement and is not considered an error.
When there are no exception conditions during space functions, forward tape motion
ends on the EOT side of the last block, filemark, or setmark and reverse motion
ends on the BOT side of the last block, filemark, or setmark.
• If a filemark or setmark is encountered while spacing over blocks or a setmark is
encountered while spacing filemarks, a Check Condition Status is returned. The
Sense FM bit is set unless a setmark is encountered and RSMK=0. The Sense
Valid bit is set, indicating Residual Length is non-zero.
The Residual Length equals the difference in the requested count and the actual
number of blocks spaced over not including the filemark or setmark. The tape is
positioned on the logical EOT side of the filemark or setmark if movement was
forward or on the logical BOT side of the filemark or setmark if movement was
reverse.
• If EOD is encountered while spacing forward, Check Condition is returned with
08h Sense Key. Extended Sense Valid bit is set, indicating Residual Length is
nonzero.
• If BOT is encountered while spacing in reverse, Check Condition is returned
with 40h Sense Key. Extended sense Valid bit is set, indicating a nonzero
Residual Length.
• If EOT is encountered while spacing forward, Check Condition is returned with
40h or 43h Sense Key. Extended Sense Valid bit is set, indicating a nonzero
Residual Length.