Back in those same mid-80s I added code to the FORMAT command to provide
an 'EXTEND' option. You could create a new, larger minidisk, the first
cylinders of which were a replica of the old one. Then you could simply
FORMAT the new minidisk, specifying the EXTEND option, and it would
magically grow in size to occupy all of the new space, with all of the
original files intact.
Now, I wonder where I stashed that code...
Ray
On 2/2/2015 19:19, Alan Altmark wrote:
On Monday, 02/02/2015 at 05:55 EST, Rick Troth
<[email protected]> wrote:
Evidently, FORMAT makes a note of the number of cylinders it block
formatted (the "low level" phase) first time around. Guessing that is
the purpose of ADTMCYL. I should have known. Sorry, Joe.
So you can (RECOMP smaller and you can (RECOMP larger, but no larger
than some pre-detected size.
You can't RECOMP anything larger than the originally formatted size. You
can RECOMP lower and back again, but no larger. And, yes, ADTMCYL holds
the number of formatted cylinders..
The protection is in place because of the allocation map. Unlike other
files on the disk, it is in a fixed location since it is written during
FORMAT and its size never changes, as that size is based on the size of
the disk. But if you add more cylinders, you add more blocks. And as you
do that, the allocation map has to grow. But it can't grow. It's
surrounded by other data.
I have to say, it's kind of fun to lean back in my rocking chair and see
my programmer id in FORMAT (DMSFOR) from back in the mid-80s. :-)
Alan Altmark
Senior Managing z/VM and Linux Consultant
Lab Services System z Delivery Practice
IBM Systems & Technology Group
ibm.com/systems/services/labservices
office: 607.429.3323
mobile; 607.321.7556
[email protected]
IBM Endicott
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