Re: Question: Normal index structure/size under 9i

From: <bchorng_at_yahoo.com>
Date: 24 May 2005 18:01:00 -0700
Message-ID: <1116981895.519398.225790@g49g2000cwa.googlegroups.com>

I think you missed a few things when you did the calculation:

You did not include rowid which is 18 bytes per row.
You did not include % free which by default is 10% - that is at least 10% of your questioned 30%. Could be more, if you have higher % free at block level.
Your reported size of 880MB probably is done on segment level which includes all the unused space within a segment.

Now, there is also a mistake in your calculation that you actually over-counted the size of each row. A 10-digit number does NOT use 10 bytes.

I believe Oracle uses bit, not byte, for number expression. So a few bytes can give you a huge number expression including signs and decimal places...etc.

Of course, there is other small overhead of block and segment header which could also add up.

Regards. Received on Tue May 24 2005 - 20:01:00 CDT