Extent allocation

Hi -

I am confused now about how oracle actually determines the size an extent should be.  I have db_block_size set at 8192 and have defined a tablespace (and tables) at initial and next extents of 128K.  When I do a show parameter db_file_multiblock_read_count it says 8.  Therefore I thought 128K would be a good number, since it is a multiple of these numbers.

However, when I check my extent sizes, I see that each extent contains 10 blocks which is 160K.

I remember reading an article some time ago about how oracle actually determines what it thinks the extent size should be.  Does anyone know of an article like this, or can anyone explain to me why it chose a different extent size?

By the way, I looked at several tables and the one common thing I noticed is that the number of blocks allocated seems to be a multiple of 5 - ie. some are 5 blocks, some 10, some 20, etc.  I don't know if that's coincidence or a big clue to the whole thing

Lisa Received on Wed Feb 07 2001 - 15:33:02 CST