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Path: utzoo!watmath!clyde!rutgers!ames!ucbcad!ucbvax!XEROX.COM!"Thomas_W._Taylor.WBST147"
From: "Thomas_W._Taylor.WBST147"@XEROX.COM.UUCP
Newsgroups: mod.computers.vax
Subject: Re: How to get rid of bad blocks on a disk (without distroying all data) ?
Message-ID: <870126-142422-4432@Xerox>
Date: Mon, 26-Jan-87 17:19:05 EST
Article-I.D.: Xerox.870126-142422-4432
Posted: Mon Jan 26 17:19:05 1987
Date-Received: Wed, 28-Jan-87 06:52:00 EST
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
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If VMS has detected a bad block in a file (via a read virtual block) it
will mark the file as having suspected bad blocks in the header.  The
suspected bad blocks are entered into [000000]BADLOG.SYS.  You can do a
$Directory/full to determine if the bit is set.  When the file is
deleted a detached process running BAD is run against the area allocated
for the file to determine if the blocks are really bad.  If they are
they are added to BADBLK.SYS.  Note that they are not entered into the
MDBSF, so they will be lost at the next INIT. 

If you suspect that a disk contains bad blocks you should be able to
write a program to do a read VIRTUAL block of all suspected blocks
(those on a disk or in a particular file).  If VMS thinks the blocks are
bad the above scenario would be followed.  I have not done this but it
seems doable.  Good luck.

			twt