In a message dated 7/29/2005 1:31:49 P.M. Central Daylight Time, [EMAIL PROTECTED] writes: >Actually I think a WRITE DATA CCW with a zero data length would cause an error.
Then I wrote: The 2105 does not specifically say that either a Write Data or a Write Key and Data with a 0 length in the CCW byte count will cause an error if inside a Locate Record Domain, so I think they would work there, but they will cause a Unit Exception error outside a Locate Record Domain. Then [EMAIL PROTECTED] wrote: >An EOF can have a key and you could then do an update write (WRITE KEY/DATA CCW) to change the key, but no access method or program I know >of supports a key on an EOF. Then I wrote: The control unit supports this bizarre combination on a formatting write. New information: I finally was able to test these I/Os. I wrote a block into the R1 position using Write CKD with KL=1, DL=0 inside a Locate Record Domain on a 2105. This worked, and the rest of the track was erased, as expected. Next I tried to update this R1 with Write KD with byte count = 1, SILI flag on, inside an LRD, and with the transfer length factor = 1 (sum of KL+DL). This worked. Next I tried to update this R1 with Write Data with byte count = 0 inside an LRD and with the SILI flag bit on. This failed with sense byte 1 saying Invalid Track Format, one reason for which is an update write operation is attempted on a record whose size differs from the record size parameter (TLF). I changed my Locate Record operands to say the transfer length factor was in bytes 14-15 of the LR operands, even though there was a 0 in these 2 bytes. This failed with command reject, msg 4, meaning invalid parameter. The transfer length factor cannot be 0 if bit 0 in the Auxiliary byte is 1 (meaning the transfer length factor is present). Thus it appears that there is no way on a 2105 ESS controller to do an update write to an EOF block unless that EOF block has a key, and then Write KD must be used. Write Data will never work on an EOF block. Bill Fairchild ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
