index blocks read one at a time or is this old info? (Sorta a myth?)

From: Pablo Sanchez <pablo_at_dev.null>
Date: Thu, 16 May 2002 11:56:01 -0600
Message-ID: <3ce3f0e2$1_19@news.teranews.com>

Howdy!

Being that we're on the topic of myths, I have in my very old Oracle 7 Performance and Tuning book that says on page 6-7: ----8-<---8-<---8-<---8-<---8-<---8-<---8-<--- How is the buffer cache managed?

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...

When the server is using index access, it always reads in one block at a time, never multiple blocks.
...

----8-<---8-<---8-<---8-<---8-<---8-<---8-<---

My take on that line at the time was that we're not sorting the database blocks within an extent. That what we are doing is maintaining a doubly-linked chain of DB blocks within the extent, which is why there is no "index_multiblock_read" (at least not in 8i) need.

Questions:

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1. In 8i and above, are our server processes still doing a single I/O at a time when running, say, an index range scan?
2. If we're doing 1), is the reason because of what I guessed?
3. If 1) again, any plans to start storing the data sorted so we can do "index_multiblock_read"s? I realize that there's a hit on changes to the b-tree because we'd have to rebalance the tree and possibly affect many DB blocks. -- Pablo Sanchez, High-Performance Database Engineering mailto:pablo_at_hpdbe.com http://www.hpdbe.com Available for short-term and long-term contracts

Received on Thu May 16 2002 - 12:56:01 CDT