Keeping the indexes in memory.

Is it possible to keep the indexes in memory, to force it. When the buffers/chache is full then first the table data must be flushed from cache then the indexes. The reason for that is, that the database I use has an unique constraint on every table and that means an index must be searched during an insert, for a possible violation of the unique constraint. With the index always in memory I hope to gain insert speed. Note: I have a lot of memory in my server so I can set the buffer count very high in case I can't do anything else then increasing the number of buffers. Regards, Albert Wisse