The ClosedFileCacheSize parameter keeps the storage objects in cache so that NSS does not need to go to disk and unpack the information again when it wants the same files.
Set this parameter to 100000 or more if you have applications on your server that consistently cycle through the same set of files and you suspect that this cache is being flushed when combined with normal server operations.
Range: 16 - 1000000. On average, each Closed File Cache entry consumes 0.4 - 1 KB of RAM.
HINT:The Closed File Cache grows up to the specified amount. Unlike file system cache, the Closed File Cache does not take the maximum amount of memory it needs from the start. It also adapts; as memory is consumed by other processes, it dynamically reduces the number of entries so the system does not become starved for memory.