SCSI FCP Transfer Requirements

Witalka, Jerome J [RV] jjw1 at po9.rv.unisys.com
Thu Sep 29 09:00:00 PDT 1994


The following text is contained in clause 7.2 of the  Fibre Channel Protocol 
for SCSI document:

"During write operations, the FCP_XFER_RDY IU indicates the amount of data 
that the Target expects to be transferred from the Initiator.  Since the 
target has planned buffering and caching resources based on that amount of 
data, the initiator shall provide precisely that amount of data"

What happens if the initiator transfers less than the amount of data 
specified because some internal error occurred (Main Storage parity error as 
an example) and it doesn't have all the data to send?  This has always been 
a sore point with me in the SCSI 1 and SCSI 2 specs.  Our current SCSI 
channel will raise Attention and pad garbage data until the Target honors 
the attention and we can issue an Abort.  We would be happier if we could 
stop the data transfer immediately and limit the amount of corrupted data on 
the medium.

Therefore, in FCP, I would like to only provide only the data I know is good 
to the Target and then send a Terminate task (preferred) or a Task Abort in 
this situation.

                                                                Jerry 
Witalka
                                                Unisys 2200 Mainframe IO 
Development
                                                               
 jjw1 at rsvl.unisys.com




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