Sub-mesh means a closed set of geometry, yes. Every texture needs his own mesh (1 model, 3 sub-meshes, 3 textures e.g).

It s not possible for me to use only one shadowmap because the model has 12 textures /12 groups of sub-meshes.
Of course i could split them but it s not nice That s the last option.

I also tried 1 shadowmap for all groups but if you activate the second UV-set in MED, you have to set a the shadomap to a mesh. Otherwise you can not use a skin mapping. If i try to set the the shadowmap for all groups not using a skin mapping, the shader should use entSkin2 with no coodinates (0,0).