Two very common types of files posted in Usenet binary groups are PAR files and PAR2 files. These are very important because they can repair corrupt files. These files both help with missing files and corruption but in two different ways.
PAR files
PAR files come in the form of .PAR, .P01, .P02 etc. Their purpose is to replace missing files. Because of completion issues, sometimes files are missing that you need. For this reason, PAR files are often posted with the files you need. Any PAR file can replace 1 missing file. However, if you have 2 missing files or a missing file and a corrupt file you are out of luck unless you can get another PAR file. Two PAR files can recreate 2 missing/corrupt files, 5 can recreate 5 missing/corrupt files etc. Therefore, a drawback of PAR files is that there might not be enough posted to replace all the files that you need to fix. In order to use PAR files, you need QuickPAR.
PAR2 files
PAR2 files are much more common and trey ar better than the early PAR files for many reasons. The main reason they ar better than PAR files is because PAR2 files replace corrupt or missing blocks of files. Therefore, if a small section of a file is corrupt, PAR2 files can rebuild it. PAR2 files look like those files in the picture beside this text. The first file, video.avi.par2, cannot actually recover anything by itself, but it can check if any blocks are missing or damaged.
So, for example, my video.avi files have 5 missing blocks when i download them. I run video.avi.par2 with QuickPar and it scans over my files and tells me that 5 blocks are needed to repair the damage. By the filenames of the PAR2 files, I can tell just how many PAR2 files I need by the last number. For example...
video.avi.vol00+01.PAR2 -> has 1 block available
video.avi.vol01+02.PAR2 -> has 2 blocks available
video.avi.vol03+03.PAR2 -> has 3 blocks available
video.avi.vol06+05.PAR2 -> has 5 blocks available
video.avi.vol11+08.PAR2 -> has 8 blocks available
video.avi.vol19+15.PAR2 -> has 15 blocks available
video.avi.vol34+30.PAR2 -> has 30 blocks available
So in order to repair a collection of files that need 5 blocks according to QuickPAR, the only file I need is video.avi.vol06+05.PAR2. Any file with more blocks will also do the trick or a few smaller files that add up to 5 or more blocks. So let's take a look at an extreme example now. I have a 243MB file (video.avi), split into 16 different parts but a whole 61 blocks are missing from my download.
Repairing with QuickPAR
So now I am in trouble, I downloaded 16 split files that make up one 243MB file, but somehow, 61 blocks are missing or corrupt. Lucky for me, the individual who posted the set of files has provided 64 recovery blocks.
I have downloaded the entire recovery set and placed the files into the same folder as my broken files. When I run any of the PAR2 files with QuickPAR, it scans and tell's me "Ready to recover using 61/64 recovery blocks".
Repairing is as easy as clicking Repair and I have gotten lucky. However, if a further 4 blocks should disappear, I am in serious trouble, because with even just one block over what's available, I cannot repair the set.
However, since I have gotten lucky this time I will now click Repair.
The recovery process The recovery process will take time based on how much repairing actually has to be done and how busy your computer currently is.
When it is finished it will tell you that the Repair has succeeded. This is important: Repairing on a regular basis is normal. even for the best of providers like Giganews, but if you find yourself not able to repair sets of files on a daily basis, then you may need to think about getting an account with somebody else.
PAR and PAR2 files are a blessing to Usenet binary groups and they will save your files many many times.
A note about PAR and PAR2 files under Newsbin Pro
Based on your settings, if you open an NZB file (we will read about them next) that references PAR or PAR2 files as well as normal files, Newsbin Pro might NOT download them automatically. Instead, it will add them to a list under the "Scratch" tab in Newsbin Pro (right beside Download). This is actually a good thing because it prevents you from wasting bandwidth by downloading files you might not need. If you find later that you do in fact need proper PAR2 files based on a QuickPAR test, simply go back to Newsbin Pro, look in the Scratch tab, find the PAR2 file(s) you need to repair and double click them. They will then be added to the download list.
PAR2 files are much more common and trey ar better than the early PAR files for many reasons. The main reason they ar better than PAR files is because PAR2 files replace corrupt or missing blocks of files. Therefore, if a small section of a file is corrupt, PAR2 files can rebuild it. PAR2 files look like those files in the picture beside this text. The first file, video.avi.par2, cannot actually recover anything by itself, but it can check if any blocks are missing or damaged.
So now I am in trouble, I downloaded 16 split files that make up one 243MB file, but somehow, 61 blocks are missing or corrupt. Lucky for me, the individual who posted the set of files has provided 64 recovery blocks.
The recovery process will take time based on how much repairing actually has to be done and how busy your computer currently is.
