In the last article about
binary newsgroups, we walked through the steps required to
download and extract files in the popular formats like ACE
and RAR. In this installment, we’re going to look at the
ways in which you can repair a file that has been damaged
during upload or is missing a file(s) that never made it
to your news server.
As you already know, when you download binaries there will
often be a large a number of files to download. If any
files are missing or damaged, your extraction will be
unable to finish, resulting in lost time and often
aggravation if you cannot find another copy of the damaged
or missing file. Another problem is that Winrar and Winace
often do not disclose the nature of the error or even the
actual file that is damaged or corrupted, making it
difficult to track down the culprit. Luckily, there are
several applications that are available to help you.
Many files posted to newsgroups are accompanied by an SFV
(Simple File Validation) file. An SFV file is simply a
list of CRC’s for for a given set of files. A CRC is a
very special number that is generated using a series of
mathematical equations. While you don’t need to concern
yourself with how they are generated, you should
understand that every file has a unique CRC. You can think
of a CRC as an identifying fingerprint for a file. The CRC
files are useful in determining if the files posted are
exactly the same as the files uploaded by the sender. By
using a third party program like Win-SFV32 (do a search on
Yahoo or Google to find this free program), you can verify
the contents of each of the files you download and locate
any that are missing or damaged. This can save a great
deal of time, and as we’ve already discovered, most of
the time you’ll be unable to determine which file is
damaged using only Winace or Winrar.
If you have been browsing through the binary newsgroups
lately, you may have seen a file called a PAR file (short
for Parity). These file are included with binary posts
along with several files named File.P01, File.P02, etc.
The PAR files should not be confused with a RAR file
although you’ll soon understand why they are so
valuable. First, PAR files are created by a program called
Mirror (see www.wehlus.de/mirror for information and
downloading of this free program). They are then posted
along with the standard RAR or ACE files commonly used.
Unlike RAR or ACE, you cannot use PAR files to simply
extract data. Instead, PAR files are used for error
correction and even detection if SFV is not also used.
Using Mirror, you can repair damaged files or even replace
completely missing files although there are some limits to
its ability. For example, if you have a PAR file and three
files named File.P01, File.P02 and File.P03, you can only
replace or repair 3 files from the set of posted files.
For example, if you are missing file File.R03 and have a
damaged file named File.r10, you are in great shape.
It’s a life saver for large downloads that often have
damaged or missing files.
In the next installment, we’ll look at how you deal with
the files that are left over after you extract them. The
files will often have names such as ISO or BIN/CUE, and
you will need third party tools to handle them. Good luck
with your downloading.
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"Introduction to Binary Newsgroups: Repairing Damaged or Missing Files"
