The requirement was that a physical block not be less than 18 bytes.
Older tape technology could not distinguish blocks shorter than 18 bytes
from tape noise.
Since an FB dataset with LRECL < 18 could easily end up with a final
block containing only 1 record (possibly even in the middle of the
dataset if extended with DISP=MOD) I would think the physical block
restriction would also have to imply a minimal LRECL of 18 as well.
Similar considerations would also apply to VB files after taking the BDW
and RDW bytes into account, and in this case there would have had to be
an minimum actual record length of 14 (including RDW) for the last
record (LRECL for VB is only the max allowed) in order to guarantee success.
I'm pretty sure all those restrictions no longer apply, since all tapes
subsystems from 3490 and later compact the logical blocks known to the
operating system into physical "super blocks" and the physical block
size on the tape is no longer under the control of operating system code.
Joel C Ewing
On 08/19/2011 06:48 AM, Shmuel Metz (Seymour J.) wrote:
In
<1240651948-1313637071-cardhu_decombobulator_blackberry.rim.net-95694995-@b12.c1.bise6.blackberry>,
on 08/18/2011
at 03:11 AM, Ted MacNEIL<eamacn...@yahoo.ca> said:
I thought there was a minimum of 18 bytes for LRECL.
No.
CIG
--
Joel C. Ewing, Bentonville, AR jcew...@acm.org
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