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Asking because my all shiny save file says it

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There are numerous factors that could have caused this, it's kind of hard to determine
Try putting your cartridge in another ds
@gmax what do you think that will do
Sometimes the corruptness has to do with the pair of the game and the console.

Also, turning off your DS while saving corrupts your data but I'm sure you already knew that
have you tried cleaning the cartridge connectors? I kept getting the same exact error on my diamond cart til I cleaned it
I belive heating cam cause the issue, I left a copy of emerald in the Sun and it got corrupted, but usually it’s just something wrong with the data saving, causing it to not save the previous data.
Hi Rizmal,

Answers on the Pokemon database typically require a source or proper list for questions like these. I’d highly recommend you to read the rules and read a few threads on meta before posting your next answer; we don’t consider this a proper answer here. I’m going to convert this to a comment.

1 Answer

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Best answer

The fundamental reason save files become "corrupted" is that they fail a checksum at some point. In the context of Pokemon save files, a checksum is a short block of data that is generated using parts of your real save data, after being fed through some algorithm. (More detail as it pertains to Gen 4 Pokemon.)

When the game loads your save data, the game re-calculates checksums based upon the save data, and compares them against the checksums it made when it saved the same data. If the checksums don't match, then the game knows the save data was altered in some way, and says it is "corrupt". (In theory, the game is capable of loading "corrupt" data, but a failed checksum suggests there is erroneous data. If erroneous data is loaded, unexpected things might happen, so the game is programmed to not load corrupted data.)

In Gen 4, the game stores two lots of save data. The first is your "recent" save, and the second is a "backup" save, which is the save prior to the most recent one. The game calculates and compares separate checksums for different parts of the save data structure, from both the recent and backup saves; more detail on that is here. But to answer this question, I'll summarise it in this way:

  1. If the game loads your recent save and finds only matching checksums, then it'll load your recent save without any problems.
  2. If the game finds a non-matching checksum in your recent save, but then finds only matching checksums in your backup save, then it will report that the save file was corrupted, and then load the backup save. This is the scenario you're asking about.
  3. If the game finds a non-matching checksum in both the recent save and the backup save, then it will report the save file was corrupted, and then you'll need to start the game over.

OK, great, but why would there be a wrong checksum (i.e. why would the save data have unexpected alterations)? Honestly you could come up with infinite scenarios for this, but here are some intuitive ones:

  1. A hardware problem caused the save data to be written incorrectly, or to be read incorrectly. This could be a literal manufacturing defect with the cartridge, or it could be physical damage to the connections within the cartridge (e.g. from dropping it).
  2. If something interrupts the game while it's saving the data, then a checksum may fail somewhere. So you should listen when it says not to remove the cart or turn off the power.
  3. If you use save modification software, then it needs to be capable of re-calculating the checksums accurately. You should know what you're doing with these, the developers don't make them 100% foolproof.
  4. Flash storage doesn't last forever and can "degrade" over time or with many write cycles. I don't think this is a problem for DS cartridges right now, don't be scared of it. (IIRC there are devices you can buy that will backup DS saves to your computer.)
  5. Cheating software like GameShark and Action Replay can also cause failed checksums, though modifications to the RAM tend to be more stable as the game will recalculate the checksum for the modified data when you next save the game. If you make any changes to the save file directly, you must be careful (that is: either avoid cheats entirely, or understand exactly what they do before you use them).

Damage to (or dirt/dust on) the exterior of the cart or the console is more likely to make the console not recognise the cart at all. There are tutorials online to help you clean cartridge terminals (usually involving alcohol). This is totally safe as long as you don't use the cartridge while there's moisture, debris, etc. on the cartridge.

Source: As above; also I study computer science + security and have done ROM hacking.

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Omg fizzypoo answered my question

Also calling the police for hacking