cdm/src/main/java/ucar/nc2/NetcdfFile.java
protected Boolean makeRecordStructure() {
    if (immutable) throw new IllegalStateException("Cant modify");

    Boolean didit = false;
    if ((spi != null) && (spi instanceof N3iosp) && hasUnlimitedDimension()) {
      didit = (Boolean) spi.sendIospMessage(IOSP_MESSAGE_ADD_RECORD_STRUCTURE);
    }
    return didit;
  }
protected Boolean makeRecordStructure() {
    if (immutable) throw new IllegalStateException("Cant modify");

    Boolean didit = false;
    if ((spi != null) && (spi instanceof N3iosp) && hasUnlimitedDimension()) {
      didit = (Boolean) spi.sendIospMessage(IOSP_MESSAGE_ADD_RECORD_STRUCTURE);
    }
    return didit;
  }
If there is an unlimited dimension, make all variables that use it into a Structure.
A Variable called "record" is added.
You can then access these through the record structure.

@return true if it has a Nectdf-3 record structure