The memory page size is not necessarily invariant. For example, NT has a 4K memory page size on the Intel platform, but an 8K memory page size on Alpha.

Anyway, there is not normally any potential memory wastage on any platform if the database block is smaller than the memory page size. The one exception would be if you were to set the hidden _db_block_cache_protect parameter. If so, each buffer in db_block_buffers will be aligned to a memory protection unit boundary (normally one page) and so some memory may be left vacant. However, if you are silly enough to set that parameter, then the memory wastage would be a minor worry by comparison with the CPU overhead! So, no, the memory page size is not directly an issue when choosing a database block size.

Is there sense to make db_block_size less than the memory page size? E.g. db_block_size = 2K and memory page size = 4K under NT, or db_block_size = 8K and memory page size = 16K under Relaint UNIX (as far as I know these memory page sizes are constant).

I am concerned about the possible 50% memory wastage because db_block_size = 1/2 the memory page size in these cases. Or Oracle works with memory itself without taking the OS memory page size into consideration?