[Info-vax] INDEXF.SYS

[jbriggs444]

On Jan 27, 6:40 am, abrsvc <dansabrservi... at yahoo.com> wrote:
> On Jan 27, 4:32 am, Jan-Erik Soderholm <jan-erik.soderh... at telia.com>
> wrote:
>
> > Babloo loves you all wrote 2012-01-27 10:21:
>
> > > Hello All
>
> > > Can I know what is INDEXF.SYS File ?
> > > What is the relation between [*SYSLOST*] folder and INDEXF.SYS File ?
> > > How to get more information regarding files present in [*SYSLOST*]
> > > folder ?
> > > How to get file identifier of a file in [*SYSLOST*] folder ?
> > > How to get information of a file with file identifier ?
>
> > > Thanks in Advance
>
> > I would be very suprised if all this is not in the documentation.
>
> WIthout getting in to many unnecesary details, let me summarize below:
>
> 1) INDEXF.SYS is the file created when a disk is initiallized that
> contains information about all of the files on the disk.  For example,
> the File ID.  All files IDs are contained here and this file is NOT
> accessible directly  (or shouldn't be).

indexf.sys is a file and can be opened for reading, file
permissions permitting.  My recollection is that the file
system does a courtesy lock, preventing it from being
opened for writing.  Any successful attempt to write to
indexf.sys is likely to be poorly coordinated with the
running file system and would tend to wreak havok with
volume integrity.

The first part of the file maps the volume home block and backup
home block.  The next part of the file is a bitmap that identifies
which
file ID's are in use.  The bulk of the file is devoted to
file headers.  Each 512 byte block in this part of the index file
contains the file header for one file on disk.  This information
includes the file owner and protection mask, the file name, a
backlink to the primary directory where the file is catalogued,
any ACL's applied to the file and the mapping pointers for all
of the file's allocated extents on the disk.  For files which are
very fragmented or with long ACL's, a chain of extension
headers is used (one block per extension header) to contain
the complete file information.

The File ID for a file is a three part value.  It contains the
relative volume number (important for files on volume sets),
the file number (an index into indexf.sys) and the file sequence
number (used to disambiguate when one file is deleted and
a new file is created using a header at the same offset in
indexf.sys).  A directory file consists of little more than a
list of file names and their associated file IDs.

When a file ID is used to find a file, the first step is to find
the block in indexf.sys (on the appropriate volume in the
volume set) pointed to by the file ID and to verify that the
sequence number in that block matches the sequence
number in the file ID.