Mark,
You are right, as your example illustrates.
What's curious to me is that if you don't specify a blocking factor in a :BUILD command, MPE/iX will now calculate one for you based on the file's record size and the sector size. For many years I wished that MPE would calculate a decent blocking factor instead defaulting to 1. Now that I finally have my wish, I find that it is no longer useful.
--Ken Kirby
Vanderbilt University
-----Original Message-----
From: Mark Bixby [SMTP:[log in to unmask]]
Sent: Thursday, September 18, 1997 11:10 AM
Subject: Re: Re[2]: Speed and KSAM
Ken Kirby writes:
> Where it is not ignored is in the way MPE stores the data on the disc. For
> example, an 80-byte file blocked at 1 will still only use 80 bytes of each
> 256 byte sector, wasting the rest. When MPE/iX goes for its chunk, it gets
> the wasted space as well as the data.
Um, no, incorrect. There is zero wasted space due to blocking factors in
MPE/iX.
Create an 80-byte file blocked at 1 record per block. Write 4 records to the
file. Use :DEBUG to display the raw sectors of the file. There is no unusable
space between any record.
:build testfile;rec=-80,1,f,ascii
:file it=testfile,old
:echo ![rpt('1',80)]>>*it
:echo ![rpt('2',80)]>>*it
:echo ![rpt('3',80)]>>*it
:echo ![rpt('4',80)]>>*it
:debug -----> requires PM capability to do this in CI
HPDEBUG Intrinsic at: a.00a7a698 hxdebug+$e4
$b ($42) nmdebug > map testfile
1 TESTFILE.PUB.XNTP 4d9.0 Bytes = 13fb0
$c ($42) nmdebug > dv 4d9.0 #80 both ------> both hex and ASCII
VIRT $4d9.0 $ 31313131 31313131 31313131 31313131 1111 1111 1111 1111
VIRT $4d9.10 $ 31313131 31313131 31313131 31313131 1111 1111 1111 1111
VIRT $4d9.20 $ 31313131 31313131 31313131 31313131 1111 1111 1111 1111
VIRT $4d9.30 $ 31313131 31313131 31313131 31313131 1111 1111 1111 1111
VIRT $4d9.40 $ 31313131 31313131 31313131 31313131 1111 1111 1111 1111
VIRT $4d9.50 $ 32323232 32323232 32323232 32323232 2222 2222 2222 2222
VIRT $4d9.60 $ 32323232 32323232 32323232 32323232 2222 2222 2222 2222
VIRT $4d9.70 $ 32323232 32323232 32323232 32323232 2222 2222 2222 2222
VIRT $4d9.80 $ 32323232 32323232 32323232 32323232 2222 2222 2222 2222
VIRT $4d9.90 $ 32323232 32323232 32323232 32323232 2222 2222 2222 2222
VIRT $4d9.a0 $ 33333333 33333333 33333333 33333333 3333 3333 3333 3333
VIRT $4d9.b0 $ 33333333 33333333 33333333 33333333 3333 3333 3333 3333
VIRT $4d9.c0 $ 33333333 33333333 33333333 33333333 3333 3333 3333 3333
VIRT $4d9.d0 $ 33333333 33333333 33333333 33333333 3333 3333 3333 3333
VIRT $4d9.e0 $ 33333333 33333333 33333333 33333333 3333 3333 3333 3333
VIRT $4d9.f0 $ 34343434 34343434 34343434 34343434 4444 4444 4444 4444
VIRT $4d9.100 $ 34343434 34343434 34343434 34343434 4444 4444 4444 4444
VIRT $4d9.110 $ 34343434 34343434 34343434 34343434 4444 4444 4444 4444
VIRT $4d9.120 $ 34343434 34343434 34343434 34343434 4444 4444 4444 4444
VIRT $4d9.130 $ 34343434 34343434 34343434 34343434 4444 4444 4444 4444
$d ($42) nmdebug > unmap 1
$e ($42) nmdebug > c
:
--
Mark Bixby E-mail: [log in to unmask]
Coast Community College Dist. Web: http://www.cccd.edu/~markb/
District Information Services 1370 Adams Ave, Costa Mesa, CA, USA 92626-5429
Technical Support +1 714 438-4647
"You can tune a file system, but you can't tune a fish." - tunefs(1M)
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