John Eells wrote:
Paul Gilmartin wrote:
On Mon, 3 May 2010 09:22:22 -0400, John Eells wrote:
If I recall correctly, it's 32760 to accommodate BDWs and RDWs for
variable data. You can find a very long post of mine in the archives
about block sizes on DASD.
I believe the BLKSIZE includes the BDW and RDWs; they aren't additional.
Hmmm...I thought they were, so that what you specified was the "logical"
block length, as is true for RDWs, but I cannot find it documented
quickly. I'll see if I can find someone who knows for sure. They are
certainly part of the physical block that is written; the question is
whether they are added to what you specify or subtracted from what you
specify.
<snip>
Turns out you're right, and I've been wrong about this for nearly 20 years.
The real reason is that the system rounds buffer space requests up to a
doubleword boundary. 32760 rounds up to 32768, which is one byte more
than can be represented by a 16-bit signed value.
--
John Eells
z/OS Technical Marketing
IBM Poughkeepsie
[email protected]
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