I am attempting to use the dissolve tool on a shapefile, but it fails with the error:

ERROR 999999: Error executing function.
Invalid Topology [Duplicate segment.]

I tried checking and repairing geometry until no more geometry errors exist. I also tried the fix topology error tool, but the topology edit tool says that no topology exists. Any ideas why this might be happening?

  • The Duplicate segment warning may be the key. Have you tried running Find Identical? (Repair Geometry doesn't look for duplicate polygons/lines.)
    – Erica
    Dec 8, 2015 at 14:55
  • Thanks for the advice. I found many duplicate rows, so I ran delete identical and got rid of them. However, the dissolve tool still failed with the same error.
    – Anthony To
    Dec 8, 2015 at 17:15
  • Importing into a GDB worked! Thanks so much for the guidance. Feel free to make an answer and I'll mark it as accepted
    – Anthony To
    Dec 8, 2015 at 19:53
  • Thank you -- I answered it more or less the same as I commented, just in case (a) both approaches were necessary to resolve it and (b) it helps somebody with a similar problem in future :)
    – Erica
    Dec 9, 2015 at 1:04

1 Answer 1


One possible solution is running Find Identical, since the error specifies "Duplicate Segment" -- Repair Geometry doesn't look for identical features, just for invalid geometries.

Sometimes ArcMap just doesn't like shapefiles as well as feature classes in a geodatabase, so converting to a GDB and then trying again is another possible solution.

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