# Magic number error in xtc file

**URL:** <https://gromacs.bioexcel.eu/t/magic-number-error-in-xtc-file/957>\
**Category:** User discussions\
**Created:** [October 14, 2020, 8:14am UTC](https://gromacs.bioexcel.eu/t/magic-number-error-in-xtc-file/957 "2020-10-14T08:14:45Z")\
**Posts on this page:** 1\
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**Author:** ![lindahl](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/lindahl/32/415_2.png) [@lindahl](https://gromacs.bioexcel.eu/u/lindahl)\
**Post date:** [October 14, 2020, 8:26am UTC](https://gromacs.bioexcel.eu/t/magic-number-error-in-xtc-file/957/2 "2020-10-14T08:26:51Z")

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The header of each XTC frame contains this number to designate it as an XTC frame. For whatever reason, your file has completely different data there. If this happens half-way through the file, you can still rescue the earlier parts by reading and then writing to another file.

Unfortunately this means your file (i.e., disk storage) is corrupted in a major way. This can be due to a number of reasons, all of which are not part of GROMACS (Bad disk, bad controller, corrupted file system, multiple processes writing to the same file without proper locking, etc.)

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