icm/HTTP/server_cache_<xx>/max_name_len 

This parameter specifies the maximum length (in number of characters) of the HTTP URIs of objects that are to be saved in the ICM cache (see also Error! No bookmark name given.icm/HTTP/server_cache_<xx>).
It is important that this value, in conjunction with the value of the parameter icm/HTTP/server_cache_<x>/max_entries, has a direct effect on the main memory requirements of the ICM cache.

For a rule of thumb for calculating the memory requirement, see icm/HTTP/server_cache_<xx>/size_MB.