Spectra Logic Spectra S50 User Manual page 141

Appendix B. Extended Copy—83h—SPC2 Specifications
Blocks field, and as many writes as possible will be performed using any residual
destination data from the previous segment and the data processed in this segment. If
the DC bit equals one, the number of blocks specified by the Block Device Number of
Blocks field will be written to the destination block device, as many bytes will be
processed as necessary for these writes to be performed, and as many blocks will be
read as necessary to supply the data to be processed.
For descriptor type code 0Dh (block->block+application client), the copy manager also
will hold a copy of the processed data for delivery to the application client upon
completion of the EXTENDED COPY command in response to a RECEIVE COPY RESULTS command
with RECEIVE DATA service action. If the copy manager supports the 0Dh descriptor type
code it also will support the RECEIVE COPY RESULTS command with RECEIVE DATA service action.
The CAT bit is described in Segment Descriptors on page 133.
The destination count (DC) bit indicates whether the Block Device Number of Blocks
field refers to the source or destination device. A DC bit of zero indicates that the Block
Device Number of Blocks field refers to the source device. A DC bit of one indicates
that the Block Device Number of Blocks field refers to the destination device.
The Descriptor Length field will contain 24 (0018h). The Source Target Descriptor
Index and Destination Target Descriptor Index fields are described in Segment
Descriptors on page 133.
The Block Device Number of Blocks field specifies the number of blocks to be
processed (if DC=0) or to be written to the destination device (if DC=1). A value of
zero will not be considered as an error. If the DC bit equals one, a value of zero
indicates that no destination blocks will be written and the only processing to be
performed is that any residual source or destination data from the previous segment
will be handled as residual data as described in Segment Descriptors on page 133. If the
DC bit equals zero, a value of zero indicates that no source blocks will be read and no
source data will be processed, but any residual destination data from a previous
segment will be written if possible to the destination in whole-block transfers, and any
residual data will be handled as described in Segment Descriptors on page 133.
The Source Block Device Logical Block Address field specifies the logical block
address from which the reading of data will start.
The Destination Block Device Logical Block Address field specifies the logical block
address to which the writing of data will begin.
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