It appears "in_memory" is not really in memory.

Question

I have ArcCatalog 10.0 from the ArcGIS Desktop 10 SP4 suite. Just now, I pulled up the interactive Python window to test some code out in the application's interpreter.>>> result = arcpy.CreateFeatureclass_management(out_path="in_memory", out_name="in_memory_junk") >>> type(result) >>> print str(result) I wasn't expecting to see the result of CreateFeatureclass to reside a temporary file geodatabase in the C:\Users\DMCGEE~1\AppData\Local\Temp\2\ directory. However, it's there, as indicated in the screenshot below. [ATTACH=CONFIG]15140[/ATTACH] I realize the documentation for in-memory workspaces indicates that "when data is written to the in-memory workspace, the computer's physical memory (RAM) is consumed", but the fact that the temporary file geodatabase is located in a temporary directory makes me think otherwise. in_memory.png image.png

MarcoBoeringa · Answer

Are you using Background Processing?
Processing in the background means sending the features you want to process over to another process and then getting a result back.
Because its another process we have to persist them to disk for ArcMap to read them on the way back.

Why o why didn't ESRI document this crucial factor in getting in_memory to work in the Help file???

I really can not find it in the main in_memory Help topic. This issue regarding background processing should be added under the "The following considerations must be made in deciding to write output to the in-memory workspace" text line. I have been struggling with this issue too.

KevinHibma · Answer

To say the Python window is a background process isn't really correct.
See this link, hopefully it'll explain background processing. You can enable/disable it and see the different results.
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00210000003q000000

DougMcGeehan · Answer

Are you using Background Processing?

I'm sure the interactive Python window in ArcCatalog is a background process. This would explain the temporary file geodatabase on disk. Are all 'in_memory' feature classes stored in this way for background processes?