Imagine a system with sufficient memory to hold all data in entry and database caches, but no support for a 64-bit Directory Server process. If hardware constraints prevent you from deploying Directory Server on a Solaris system with 64-bit support, size caches appropriately with respect to memory limitations for 32-bit processes. Then leave the remaining memory to the file system cache.
As a starting point when benchmarking performance, size the entry cache to hold as many entries as possible. Size the database cache relatively small such as 100 Mbytes without completely minimizing it, but letting file system cache hold the database pages.
File system cache is shared with other processes on the system, especially file-based operations. Thus, controlling file system cache is more difficult than controlling other caches, particularly on systems that are not dedicated to Directory Server.
The system might reallocate file system cache to other processes.
Avoid online import in this situation because import cache is associated with the Directory Server process.