Dissolve error in Model Builder ArcGIS 10.1

[MatthiasMohaupt]

Hello,
I´m trying to do a simple dissolve task in Model Builder 10.1 which worked fine in ArcGIS 10. It also works as desired when I use the tool outside the Model Builder. Strangely, besides the fact that the number of features is falsely increasing after running dissolve, the output is singlepart although I checked the multipart option and the input is a multipart feature class.
Any suggestions?
Thanks!

[MartynMcGuinness]

I've had the same problem with the Dissolve Tool since moving to 10.1.  I first noticed it 2 weeks ago in a model built in 10.0.  After a bit of time spent looking for solutions I rebuilt the model in 10.1 and it seemed to solve it. 

However the problem had recurred again today in another basic model and the rebuild option has not worked this time.  After testing the tool inside and outside of models I have seen the multipart problem also occur when running outside of a model - but not every time, and am unable to reproduce the error consistently.   

When trying to repeat the steps of the model with just the standalone GP tools the multipart feature worked one time, but then a while (after a few other select and dissolve tools) later failed to work on the same input with the same Environments??  (Image of GP results attached)
The only thing so far that I can see that may be consistent is the select tool?  The multipart dissolve has worked when I put a definition query on the layer and then Dissolve, but fails to work if I use the Select tool to create an intermediate selection matching the definition query, and then dissolve.  And then fails to work subsequently after the select has run?  Not 100% sure on this but I will do some more testing over the weekend and see what more comes of it. 

Hopefully we can resolve this issue soon as the dissolve tool is my most commonly used GP tool.

[MartynMcGuinness]

I have been doing more testing and most of the time I am unable to get Multipart polygons out of the Dissolve tool whether it is run in a model, as a stand alone tool or activated through the python window in ArcMap.  

The only way I can get it to work is by using a stand alone Python script - guess I will have to brush up on the python skills and rebuild everything in Python!

[bridgetsullivan]

I am having dissolve issues with both python and using the dissolve data management geoprocessing tool.  They both work with no Dissolve Fields(s) options checked but fail when fields are selected.  Script worked at version 10 but is not working at 10.1 sp1

[tarohosoe]

Try using the dissolve tool from inside ArcCatalog instead of ArcMap. This works for me.

[DavidBoyd]

For what it's worth, I'm having the same problem.  I just created a model including a dissolve (10.1) based on a numeric field.  It's runs fine without error, but the resulting data isn't dissolved into multipart shapes even though that option is checked.  I can run the dissolve outside of the model successfully, but this kind of makes my model useless.  Has anyone found the cause of this...or is it maybe a bug?

[curtvprice]

Try using the dissolve tool from inside ArcCatalog instead of ArcMap. This works for me.

This makes me suspect the issue may involve data types. In ModelBuilder, often you are creating output in the scratch workspace (intermediate data) as part of a processing chain. In ArcCatalog, you may be working with a differerent scratch workspace.

Is it possible the problem is with shapefile workspaces (folder) not giving the same dissolve results as geodatabase workspaces?

I see no mention of service packs, and the thread dropped off a whiel back. Perhaps an update to 10.1 SP1 or 10.2 would help?

[MichaelVolz]

Does anyone know if this issue still exists in ArcGIS v10.2.x?  I ask because a model in modelbuilder using the dissolve tool is not working in v10.2.0.

Was anyone encountering this problem using SDE data that was stored using ST_Geometry?

[MicheleH_DNReply]

I have not had this problem since moving to 10.2.  If you can move I would say go ahead.