Each search on the wiki reads the whole index directory. Each search starts with a listing of this directory to find the index files, scanning the index directory each time is time consuming with a constant series of disk access.
This special feature when set to a different value than 0 register the list of index files in a cache file and read this file instead of the directory. The value indicates the lifetime in seconds of the cache file. This feature is recommended on a large wiki or when you have a poor disk access.
When this cache is used a normal search only uses file_exists 1 or more times, and not readdir all the directory. The wildcard search uses the cache file for getting all used word lengths if it is enabled.
0