Jeff writes:
> Since MPE doesn't deal (internally) with less than a page, you've got
> 4096 bytes as the minimum atomic read/write.  And 4096/187 = 21.9, so at
> least start at blockfactor 21.

But don't get too hung up on blocking factors because they do only apply to
CM file types (which may be only RIO and CIR these days and to some extent
CM KSAM).

For all other file types the blocking factor is ignored by MPE as there is
no wasted space between records (the blocking factor is effectively
infinite) and MPE itself does not perform any operations in units of blocks
(everything is memory mapped I/O with the hardware dealing in units of 4KB
as Jeff says and I/O generally happening in multiples of the 4KB page size.

Exceptions are NOBUF/MR operations which I think simulate blocks, and of
course Image does its own internal blocking which you still have to pay
attention to.

If you :STORE a file with the ;TRANSPORT option (to create an MPE/V
compatible tape) :STORE will transform the files into blocked format based
on the blocking factor assigned at :BUILD time.

G.

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