On Apr 2, 2008, at 16:04, Schuh, Richard wrote:
Historically in the O/S360-z/OS line of systems, a zero length
record on
disk has indicated End-of-File for either PS or PO organizations.
In the
PDS, each member is a PS file, so there are potentially many zero
length
records in a PDS. OS Simulation knows how to handle them, but, as
noted,
CMS does not like them.
Sigh. A couple specious arguments. First, remember that hardware
types say "record" where software types say "block".
o So we're really talking about an empty block.
- for RECFM=V, an empty record has at least an RDW, so only a block
containing no records can have zero length.
- For RECFM=F, an empty block either contains zero records, or
LRECL=0. May we agree to disregard the latter case?
In either case, a file can be unambiguously terminated by
an empty block, which must contain no records.
o Does CMS, either in SFS or MDFS, terminate files with any sort of
End-of-File, or does it rely on pointers in the directory?
o When last I looked (some decades ago) CMS didn't separate MACLIB
members with any sort of End-of-File. Rather, it used a specific
data pattern in a record. (I think this engendered a problem of
unintended detection of End-of-Member).
-- gil
