For one, two, and n-level dimensions, you can use the rundimdata command line program to import data before the actual PPM import takes place. In this case, the values are imported as pairs in the form <key-description> for each dimension level. Note that a key must be specified, while the description is optional.
You will find detailed information about importing dimension values for text dimensions in advance of the actual PPM import in the PPM Data Import manual.