Our static data object is created. Some of the methods (not all) are called and data is saved to the static. Before each frame is processed, the state of the decoder is written to the FRM file. That’s where PD comes into play. It is used to store data from our static to the FRM file using a byte array as an intermediary. This is done to save the state of the static at ENTRY to each frame. After the frame is processed, OD is called to give us a chance to remove any data we didn’t really want to save. In summary, PD is called only during the compile phase and before each frame is processed.
OD is called only during the compile phase and after each frame is processed. Remember, our static and the byte array are two different things. When OD is called, we don’t mess with our static. We only remove data from the BYTE_ARRAY that we know we won’t need during reconstruction.