Path: utzoo!mnetor!uunet!btni!hdr!eric
From: eric@hdr.UUCP (Eric J. Johnson)
Newsgroups: comp.unix.wizards
Subject: Reading 12255 byte tape blocks on System V
Message-ID: <741@hdr.UUCP>
Date: 5 May 88 13:26:13 GMT
Reply-To: eric@hdr.UUCP (Eric J. Johnson)
Organization: Amperif Corporation.  Omaha, NE
Lines: 38
Keywords: 9-track tape driver problem

I am having trouble reading 9-track tapes that have a blocksize greater than
8192 bytes on my AT&T 3B15 running System V 2.1.1 equipped with a standard
1600 bpi 9-track 1/2 inch tape drive.

Specifically, I have about eighty 1600 bpi tapes, each blocked at 12255 bytes 
which need to be loaded.  I can read the first 8192 bytes of each block
using dd as follows:

	dd if=/dev/rmt/0m ibs=8192 of=tapeout

But, I lose the last part of each block.  When I try using the following
dd command:

	dd if=/dev/rmt/0m ibs=12255 of=tapeout

dd returns the following message:

	dd read error: No such device or address

and I get no data in my output file. 

One thing that confused me was that my copy of the TAPE(7) manual says I
can have a buffer size up to 32768 bytes when using the "raw" interface.

I called AT&T Software Support with the dd failure and 32768 byte buffer
limit question and was politely told that yes, the blocksize limit was
indeed 8192 bytes.  The 32768 byte number was the record size limit.

Well, now that I've been set straight by talking to Software Support,
does anyone have a work-around/solution to this limitation?

PS: No, the tapes are not available in a smaller blocksize.

-- 
Eric J. Johnson         UUCP: eric@hdr.UUCP || ...!{ihnp4, codas}!hdr!eric
Amperif Corporation.    CIS: 72460,11  BIX: ericj

Just a minute, Just a minute, The AE-35 unit will go 100% failure in 72 hours!