[TUHS] Were all of you.. Hippies?
wes.parish at paradise.net.nz
Mon Mar 27 09:29:37 AEST 2017
To give an example of what one other operating system means by records, I point you in the direction
"Windows and *NIX file systems are based on hierarchical directory structure. Basically, you have one
root directory and you can create directories (sometimes called folders) or files under that root
directory. Mainframe disk files are very different to this hierarchical approach."
"MVS datasets always have record lengths. MVS access methods read and write records in physical
blocks. A block is made up of one or more logical record. This diagram shows the block sizes and
difference between fixed block and variable block data sets.
The access method is responsible for splitting the block into logical records and passing the record to
the program. Although a program can handle breaking the blocks into logical records, this task is
normally done by the access method. A record length can be fixed or variable."
If you're familiar with the Network and Hierarchical Database systems from practical experience or from
working through non-relational dbms books, this all looks very familiar. Essentially such file systems
are hierarchical dbmses. As should be expected from MVS's derivation from batch systems.
I don't know anything about the DEC VAX VMS file system. I was meaning to learn a few years ago, but
other things happened ...
Quoting Larry McVoy <lm at mcvoy.com>:
> On Sun, Mar 26, 2017 at 07:31:30AM -0400, Ron Natalie wrote:
> > Maintaining records iwas far from unheard of at the time networking
> showed up in UNIX. Think about how the UNIX tape driver works.
> I think that unix "records" are just a struct in binary in the file.
> That's a
> little different (a lot different?) than what most operating systems
> mean by
> records. Unless I'm mistaken.
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