[Info-vax] ODS-5 data/file recovery

[Stephen Hoffman]

On 2013-02-16 13:32:12 +0000, MG said:

> What can I best do?  I have no gotten any further.  Is there perhaps
> anything besides DFU out there, in terms of 'tools', that can handle
> FILES-11 ODS-5?

Choices, in no particular order:

1: Give up on that file, and move on?  This depends on how 
irreplaceable the data in that file really was; what it will cost you 
to recreate the contents.

1a: Most of us have made and have learned from this and similar cases — 
as this will not be the only time a file goes missing with OpenVMS, or 
any other operating system — and will look at and potentially improve 
the backup strategy.  (Each time I encounter one of these cases, the 
more I value operating systems that provide integrated backup 
mechanisms, and applications with integrated backup.  With OpenVMS, 
there's no template, no automatic operation, and you get to roll your 
own.  Which is a PITA.  But I digress.)

1b: shift to a computing platform with the tools you expect and need?  
CIFS has long been "fun" to deal with on OpenVMS.  OpenVMS disk 
services aren't particularly stellar implementations, either; the 
CIFS/Samba port is old, partial, ill-documented, and complex.  Some of 
my experiences with it are at <http://labs.hoffmanlabs.com/node/1350>.  
This also includes (preferably integrated) backup tools and data 
recovery tools, as there are a variety of circumstances where files can 
end up unavailable, regardless of the operating system.  Other 
platforms can have easier and newer and variously better tools.

2: Read the on-disk structure (ODS) specs, and scrounge up, or roll 
your own tools?   Treat this as an opportunity to learn the innards of 
the ODS-2 and ODS-5 file systems and data structures, and the 
programming languages and tools.  As disk structures go, ODS-2 and 
ODS-5 are not particularly demented, and the ODS-2 portions are 
documented, and the data structure declarations are all available in 
the libraries.

2a: The ODS2.DOC text file is the starting point for this quest, if you 
don't have access to Kirby's book.  Also see 
<http://labs.hoffmanlabs.com/node/209>.  With the exception of an 
identifying constant in the volume header to differentiate ODS-2 from 
ODS-5 and the addition of FI5DEF structures used for filenames that 
don't fit into the existing FI2DEF data structures, ODS-2 and ODS-5 are 
basically identical on-disk.  Subsequent to the ODS2.DOC text file, 
both acquired longer bitmaps at V7.2, and both can have a GPT 
<http://developer.apple.com/library/mac/#technotes/tn2166/_index.html> 
on Itanium which caused some of the headers to be relocated 
<http://labs.hoffmanlabs.com/node/112>.  Dig the starting block 
addresses and the block lengths out of the header for each extent, and 
dig the extents out of any extension headers that might be involved, 
and read them in.

3: Hire somebody to recover the files for you?   This usually won't be 
cheap, so see 1 above.

Caveat: Any recovery of the file may or may not get back all the data, 
particularly if the volume wasn't taken offline before the header 
block(s) or data blocks were reused.  Depending on what was reused, you 
might not get anything back.


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