{Error codes from mmp$mm_write_modified_pages.

  TYPE
    mmt$write_modified_pages_status = (mmc$wmp_io_initiation_reject, mmc$wmp_io_complete, mmc$wmp_io_active,
           mmc$wmp_volume_unavailable, mmc$wmp_io_errors, mmc$wmp_server_terminated);
