Directory Server runs as a multithreaded process, and is designed to scale on multiprocessor systems. You can configure the number of threads Directory Server creates at startup to process operations. By default Directory Server creates 30 threads. The value is set using the dsconf(1M) command to adjust the server property thread-count.
The trick is to keep the threads as busy as possible without incurring undo overhead from having to handle many threads. As long as all directory data fits in cache, better performance is often seen when thread-count is set to twice the number of processors plus the expected number of simultaneous update operations. If only a fraction of a large directory data set fits in cache, Directory Server threads may often have to wait for data being read from disk. In that case you may find performance improves with a much higher thread count, up to 16 times the number of available processors.
Directory Server uses file descriptors to hold data related to open client application connections. By default Directory Server uses a maximum of 1024 file descriptors. The value is set using the dsconf command to adjust the server property file-descriptor-count. If you see a message in the errors log stating too many fds open, you may observe better performance by increasing file-descriptor-count, presuming your system allows Directory Server to open additional file descriptors.
The file-descriptor-count property does not apply on Windows.