Re: Table not reusing deleted space

Leng,

I recall a similar scenario some months ago. It had to do with the average row size (quite large) and the block size. The average row size was just under 1/2 of the block size, so the chances of a new row finding a spot in an existing block was slim. Add in that there is a limit (5 I think) of blocks on the freelist that a transaction will attempt to allocate space in before it says "I can't find a block with enough free space so I'm going to allocate a new extent.". I think we looked at dba_tables.avg_row_len and dba_tables.avg_space_freelist_blocks. (?) A quick calculation (1048576k /200000) indicates that your average row length is over 5k. If you have 8k blocks, this means an average of 1 row per block (perhaps less depending on the variance in row length).

Daniel Fink

"Kaing, Leng" wrote:

> Hello everyone,
>
> Env: 8.1.7.4, SunOs 5.8 64 Bit
>
> We seem to hitting bug 1262161. The bug seems to imply that tables with triggers behind them do not reuse blocks on the freelist. We have a table that should only use 1G (num_rows * avg_row_len), but is actually using 4.1G and growing in size!! It is subject to high inserts, deletes and updates. But the resultant number of rows is around 200K rows. The insert is just a normal insert, no APPEND hint is used. Updates do not really expand the rows.
>
> We've changed PCTUSED from 40 to 70 to no avail. The table does not seem to reuse the deleted space.
>
> In trying to prove this error in our environment I've created 5 test scenarios but was never able to reproduce the problem. It only exists on our production database. I'm stumped. Has anyone encountered this problem?
>
> Or can someone explain to me why our production database is not reusing the space deleted and placed back on the free list? I should also add that the table in question is a master table of a snapshot.
>
> TIA,
>
> Leng.
>
> ----------------------------------------------------------
> Leng Kaing
> Email: leng.kaing_at_team.telstra.com
> Phone: +61-3-9203-7589
> Mobile: +61-417-371-348

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Author: Daniel Fink
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