code: protected RecoverableUnitImpl getRecoverableUnit(long identity)
      {
          if (tc.isEntryEnabled())
              Tr.entry(tc, "getRecoverableUnit", new Object[] { identity, this });
  
          RecoverableUnitImpl recoverableUnit = null;
  
          // Only attempt to resolve the recoverable unit if the log is compatible and valid.
          if (!incompatible() && !failed())
          {
              recoverableUnit = (RecoverableUnitImpl) _recoverableUnits.get(identity);
          }
  
          if (tc.isEntryEnabled())
              Tr.exit(tc, "getRecoverableUnit", recoverableUnit);
          return recoverableUnit;
      }
docs: Retrieves a RecoverableUnitImpl object, keyed from its identity from this
  classes collection of such objects.
  
  @param identity The identity of the RecoverableUnitImpl to be retrieved
  
  @return RecoverableUnitImpl The required RecoverableUnitImpl