The tile cache is the place where tiles whose lock counter
has returned to 0 are stored. The tiles in the cache are eligible
for unloading if memory is needed for loading new tiles.
The cache can be shared among several layers, which means
that loading a tile in a layer can cause that tile to be unloaded
in another layer.
The
IlvDefaultTileCache class implements a cache algorithm consisting of
a simple LRU (Least Recently Used) structure that unloads first the
tiles that have been visited the least recently.
You can, however, implement another algorithm that will
be more efficient with respect to the specific nature of your application.
Here are a few criteria you might take into account when implementing
a new backup cache algorithm.
Unload first the tiles that require
a larger number of pan or zoom operations to be reached from the current
position.
Unload first the tiles that have taken
the longest to load.
Unload first the tiles that contain
the largest number of graphic objects.