Setting the buffer cache sizes using the server startup options -iqmc and -iqtc has two important advantages:
It allows you to set cache sizes greater than 4GB. These larger cache sizes are not allowed on 32-bit platforms, but are recommended on 64-bit platforms.
It allows you to modify cache sizes if you have set the database options larger than your system can accommodate, so that you cannot open the database.
Whether you use the database options or the server options, you must restart the server to change buffer cache sizes. The -iqmc and -iqtc server startup options only remain in effect while the server is running, so you need to include them every time you restart the server.
