An application can use PARAMESH in one of 2 ways. It is important to understand this design choice.
The first approach (Strategy I) is to reserve permanent guardcell storage at the boundaries of each grid block. This simplifies the use of PARAMESH but can require a large memory overhead, particularly in 3D or when your application uses a high order numerical scheme.
The second approach (Strategy II) does not reserve permanent guardcell storage at the boundaries of each grid block. This reduces memory overhead but at the cost of some additional complexity in the applications flowchart.
If you are a new PARAMESH user we recommend that you begin by following Strategy I. Then, when you have gained familiarity with PARAMESH you can straightforwardly modify your application to use Strategy II, if memory overhead is an important consideration.
Detailed `how to' instructions on implementing these two strategies are provided in other sections of this User's Manual.