Re: impact of freelists on inserting ?

There is (virtually) no storage impact due to freelists, it simply means that there are more linked lists set up in the segment header for processes to acquire free blocks from, which means less frequent calls to 'add more empty blocks to free list'.

Your stats suggest that there may be a need to increase the number of rollback segments (which you may choose to 'fund' by decreasing the size of the segments).

This in turn may be an indication that you have a need to increase freelists even more (or perhaps set it high on a table / index where it is still at the default).

If you want to narrow down where the buffer busy waits are, you should look at x$kcbfwait (see note on my web site) to find out which files the waits are associated with.

Changing db_writers is unlikely to affect these stats - buffer busy waits and write complete waits are pretty much independent of each other.

--

Jonathan Lewis
Yet another Oracle-related web site: http://www.jlcomp.demon.co.uk

tedchyn_at_yahoo.com wrote in message <7uo6pb$qjl$1_at_nnrp1.deja.com>...
>Sir, I have following waitstat in one heavy inserting instance. when I
>increase dbwr from 1 to 4. waitstat number did not change very much.
>I found out freelists on table was setup to 10. generally you set
>freelists to > 1 (may be 2) for heavy inserting table. my question is
>what kind negative impact high freelists has on a table aside from
>more storage requirements ?
>
>thanks in advance Ted
>
>
>CLASS COUNT TIME
>------------------ ---------- ----------
>data block 350262 231895
>sort block 0 0
>save undo block 0 0
>segment header 5701 16139
>
>
>Sent via Deja.com http://www.deja.com/
>Before you buy.
Received on Fri Oct 22 1999 - 03:17:42 CDT