Solution or Workaround
Why do I get this error when I run shp2sde using no -k option?
SDE code 959: *** INVALID_ERROR_CODE ***
In $SDEHOME/etc/dbtune.sde, in the #DEFAULTS keyword section, one of the tablespace names is not spelled correctly, that is, it does not match the name of the desired tablespace name.
Code 959 is really referring to Oracle error 959, no such tablespace, it is not an SDE error.
You can reproduce this locally by changing the A_TBLSP parameter under the DEFAULTS keyword in then dbtune.sde file to a non-existent tablespace and trying to load a layer with shp2sde, using no -k option.
Another side to this problem was also seen when trying to load data into a new feature class using ArcCatalog. A pop-up windows appears, but there is no error text.
This is a known problem.