The first is within the PersistenceManager and is the Level 1 Cache. There are 3 available implementations of a Level 1 Cache here :- SoftRefCache, WeakRefCache and HardRefCache. They provide varying degrees of object retention during the garbage collection process.
The second is across multiple PersistenceManagers within the same PersistenceManagerFactory, and is the Level 2 Cache. There is one implementation of a Level 2 Cache here :- DefaultLevel2Cache. Alternatively, there is the TangosolCache plugin that can be used in conjunction with the commercial Tangosol Coherence product.