Shape_area and shape_length field disappear when exporting to a .sde

[DanaYoung]

Can anyone explain why these two fields disappear when I export/import the feature class from a file geodatabase (.gdb) to a server geodatabase (.sde). I have definition queries that use these fields, I tried to create new fields, but then the calculate geometry was unavailable.

[DanPatterson · Accepted solution]

Fundamentals of field calculations—ArcGIS Pro | Documentation 

You would have to calculate area/length fields under a different name since the file geodatabase maintains those fields.

[VinceAngelo · Accepted solution]

Long, long ago, Arc/Info had LENGTH field on LINE coverages, and AREA and PERIMETER on POINT and POLYGON (because they shared the ".PAT" suffix). Those properties were retained as methods on geometries in SDE, ArcSDE, and enterprise geodatabase, depending on the storage (and topology class).

In the meantime, file geodatabase was created, and it exposed these meta-properties as fields, but the units are Cartesian, so they're not completely useful in all use cases.

If you want to keep these phantom fields across datasets, it's often best to create your own fields to preserve them (but then you have to update them if the geometry changes).

- V