The indices are completely regenerated at the end of the PPM import after all process instances have been updated on the analysis server. This means that the selection of dimensions on which there is an index and their configuration is updated on the analysis server with each PPM import, compression, or deletion. Even if the PPM import does not find any new data to be imported, the indices are regenerated with the currently configured settings.
Restarting the analysis server from the recovery file also updates all indices.