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From: paul@ism780b.UUCP
Newsgroups: net.micro.cbm
Subject: Re: 1541 reliability update
Message-ID: <29@ism780b.UUCP>
Date: Fri, 27-Jul-84 00:21:22 EDT
Article-I.D.: ism780b.29
Posted: Fri Jul 27 00:21:22 1984
Date-Received: Tue, 24-Jul-84 03:33:38 EDT
Lines: 32
Nf-ID: #R:iddic:-175000:ism780b:26500002:000:1702
Nf-From: ism780b!paul    Jul 20 11:26:00 1984

> I always thought that scratching a file isn't SUPPOSED to update the BAM.
> If it did, the trick of un-scratching accidently scratched files by setting
> 2**7 of byte zero of the directory entry wouldn't work after any further
> file allocation, because some of those blocks might have been reused.

The trick may well NOT work if any file allocation has been done since the
file was scratched, because the BAM IS (usually) updated.  For the same
reason, you'd better run the "validate" command after unscratching a file,
or DOS will think the blocks in it are still available.

> For those of you that don't realize what "validate" does, it searches
> through all unscratched files on the disk, rebuilding the BAM from the
> file chains. That's why you can't validate a disk with type relative
> files on it: the side-sectors will be treated as unused.

Basically right, but I think you are confusing "relative" and
"random" files.  I have "validated" disks with relative files,
and it sure SEEMED to work.  According to the wretched 1541
manual, only "random" files are incompatible with the validate
command.  This makes sense, because "random" files are not really
files at all, just a way to access the drive as an array of
blocks; relative files are real files in that they have a name,
sector links, etc.

Paul Perkins    --      INTERACTIVE Systems
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