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How to Prevent and Overcome Save File Corruption

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fergusmo88's Avatar fergusmo88
Level 28 : Expert Architect
So you log on to Minecraft one day, and your save file is missing-or it is extremely laggy to becoming the point of unplayable. What do you do?

If your save does not show up in the list of saves, it is because of level.dat corruption. The level.dat file is found within the save folder (at %appdata%/.minecraft/saves) and is the most important file of the game. It dictates your seed, location, and inventory. Without it, a save ceases to become recognized as a save. There is no way, as of now, to overcome level.dat corruption, but a quick fix would be to load an earlier level.dat from a backup. That way, your world is unchanged, just your inventory, location, and time of day.Simply use TMI/SPC to restore your previous inventory. If you're strictly vanilla, however, you can just load a backup (by copy and pasting it in your saves-duh!). Don't have a backup? In Windows 7 you can restore previous versions by right clicking on a file and choosing "restore previous versions" on the menu. Not Windows 7? Tough luck, because at this point you will have to resort copying and pasting the level.dat from another save. If you do that, then the biomes will all be messed up and new terrain generation will be weird-but at least it will allow you to keep your save. As a last resort, you can find your seed using F3, use a level.dat from another world, and then find a way to change the seed.

Preventing level.dat corruption is as easy as it is overlooked. First, don''t close Minecraft abruptly! Don't turn off your computer or log off while Minecraft is running, and NEVER close Minecraft in the inventory screen or when the esc. menu displays "saving level" (it is okay to close Minecraft at the menu after the world has been saved). I know, you don't want your parents to find out you're playing Minecraft 5 hours a day, but what would you want: being discovered or lose your world you've been working on for a total of 5 x 365 = 1825 hours? Another commonly overlooked thing to do is: BACKUP SAVES OFTEN! Make at least two (one on your harddrive, another on a USB, so if your computer gets infected by a virus or something your save won't be lost forever), and keep a reserve level.dat at all times in case all your backups are corrupt. Finally, DON'T, FOR THE LOVE OF GOD, USE MCEDIT WITHOUT CLOSING MINECRAFT (not even at title screen, because the save doesn't completely close at the screen). It will not only corrupt your level.dat, but also your regions, which brings us to our next point...

Over 75% (OVER 9000) of world saves corrupted are because of level.dat corruption. However, there other, more hidden reasons accoutable, too. One of these is, well, region corruption. This is when a region gets misplaced or its files have been corrupted, causing the player to freeze at the edge of the corrupted chunks and making said chunks laggy to the point of unplayable. In this case, if it's an unused chunk(s), use MCedit to delete the chunks. They will regenerate when you come close to them. This is even better in a chunk with mined diamond or explored cave, as it will allow you to mine said diamond/cave twice! However, if you built something on that chunk and do not want to lose it, copy your structure to another location/make a schematic, and then delete the chunks. Afterwards, you can place your structure back.using "Import" in MCedit. NEVER DO THIS WHILE THE GAME IS RUNNING. Other than that , follow the level.dat corruption tips; use backups, etc.

You go outside, and see sheep/cows/whatever falling from the sky (hopefully not creepers). Your framerate drops to 0 fps. What do you do? Erratic animal spawns (passive only) are caused by much the same things as the two problems above, but this problem in particular is harder to solve, as the shock of the situation gives you little time to act before the game crashes. However, the solutions are obvious. Use /killall in Single Player Commands, which kills all entities (keep using it if you have to). Also, you can delete all entities in MCedit, by selecting an area and then choosing "delete entities" on the left menu. You can also delete the chunks, but that's not advised because the chunks won't have enough time to generate when you log back on, and you'll fall through the world. Other than that, you can simply walk away, if you have time, or kill yourself. If worst comes to worst or you're lazy, load a backup save/level.dat file which places you far away from the spawns.

Look, we really can't go further without discussing chunk errors. Chunk errors are when chunks fail to load-that means that you can't go into them and fluids don't flow into them. They're much more common on SMP, but more serious in SSP (in SMP they're client-side so you solve the problem by logging out and logging back in, but in SSP you can't do that). The only real way to solve chunk errors without backups is to delete the chunks affected by MCedit. If you have structures built, then restoreing previous versions or backups are the only options available to you. However serious the chunk error is, though, you can take solace in knowing that chunks errors are entirely Minecraft's fault, and are not cause by closing Minecraft suddenly, etc.

If your problem is not listed, feel free to comment on the comments section and write out your problem. I'll try to the best of my ability to help you.

That's it! Here are some more tips, in case the above doesn't help.

1. In pre-1.8, if a skeleton lands an arrow on a block of ice and you break that ice, the game displays a "saving chunks" screen and crashes, and the world cannot be played anymore. The only way to fix this was to use a backup, or by restoring previous versions.

2. Experincing sudden lag on your noramlly 500 fps computer? The problems could be chunk corruption or erratic animal spawns. Remeber, corrupted chunks can look normal, so the only surfire way to fix this is to delete all chunks affected. Copy all structures in the area into an MCedit schematic if you don't want to lose yur buildings. Killing yourself or moving away might offer temporary aid, but it doesn't fix the root of the problem.Even using backups won't help, as some chunks in pre-1.8 just become corrupted as they generate (not sure about this one, but happened to me several times).

3. Bad chunks are chunks where entites can't move. Should you enter a bad chunk, your screen will shake uncontrollably, and you won't be able to move. Treat bad chunks the way you would treat corrupted ones.

4. Trivia...In Legend of Zelda: Skyward Sword (yes, I'm a Zelda fan), there is a gamebreaking bug. If you learn the Thunder Dragon's song first, the events in Faron Woods and Eden Volcano will not happen, causing the player to be unable to progress. That was random.

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