[Info-vax] Out of diskspace :(

[Paul Sture]

On Sat, 19 May 2012 09:42:01 -0700, hb wrote:

> On May 19, 5:38 pm, Johnny Billquist <b... at softjar.se> wrote:
>> I would not expect VMS home blocks to be located on different blocks
>> depending on the size of the disk. You learn something every day.
> 
> Usually the home block is in the second logical block: LBN 1. This LBN
> is called the primary home block. If the primary home block is not found
> (corrupted or overwritten by whatever), secondary home blocks are
> searched at different LBNs of the disk. The secondary home block LBNs
> are derived from the size of the disk. This is called the secondary home
> block search sequence.
> 
> ODS2/5 for OpenVMS/I64 uses a GPT (GUID Partitioning Table ) which
> occupies at least LBN 0 and 1. So there are no primary home blocks for
> these disks.
> 
> Also, according to the "VMS File System Internals" book, the file system
> must be able to allocate two good home blocks. It's not explained how
> the second good home block is found. Home blocks are in the VBNs
> 2,...,cluster_factor*3 of INDEXF.SYS. For a valid home block in LBN 1
> one could get another home block from INDEXF.SYS without depending on
> the disk size. But it seems the file system rather looks for another
> good home block on the search sequence than trusts what it finds at LBN
> 1, which makes sense to me and which may explain "not finding the home
> block" after the disk size changed.

Thanks.  I have a feeling that one of the error messages I saw indicated 
that the system couldn't find the _alternate_ home block.

Here's part of a post I made on 3-Apr-2012:

http://bit.ly/KkWoiN

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Newsgroups: comp.os.vms
Von: Paul Sture <p... at sture.ch>
Datum: Tue, 3 Apr 2012 14:23:10 +0200
Lokal: Di 3 Apr. 2012 13:23
Betreff: Re: how to extract and install content from vms073lp.zip

<snip>

That's how I understand it too.  In the SimH context, I accidentally
changed the value of RAUSER=n by factor of 10 for an existing disk and
when I tried to mount it from VMS, unsurprisingly I got a message about
the bitmap being corrupt.

I've never seen a message about BITMAP.SYS being fragmented before :-) 
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-- 
Paul Sture