Copying existing records over an SDE feature class fails with the following error:
Error: A failure occurred copying features. The index passed was not within the valid range.Copying records is done by using the context menu from the Catalog tree or using the Copy tool in the Data Management toolbox. For more information about copying records, refer to the following web help document, ArcGIS Desktop: Copying feature datasets, classes, and tables to another geodatabase.
Copying records into an SDE feature class requires matching schemas. For example, if one of the layers has a field with the name, ID, and contains a LONG data type, the copied data must contain the same field ID with LONG data type. A mismatch of the data type between the two features causes the error.