Re: Physical reads on Tables cached in KEEP_POOL

On 25 Feb 2005 12:14:36 -0800, "Gordon" <gordon_t_wu_at_yahoo.com> wrote:

>Hello,
>
>
>
>I'm getting a bouch of physical reads from a table that has been put
>into the KEEP pool. I've check that the KEEP pool does have sufficient
>memory to hold the tables cached in them.
>
>>From Statspack I see the SQLs causing physical reads are INSERT
>statements. Why does INSERT statements perform physical reads on
>tables that have been cached in KEEP pool? I'd think it would only
>need to perform physical writes.
>
>I'm running Oracle 10g on SUSE Enterprise 9
>
>Thanks

First of all: the KEEP pool only guarantees the data is on the cold end of the LRU list. The KEEP pool itself is not excluded from the LRU algorithm.

Secondly: a client session NEVER issues a physical write. Physical writes are handled by the DBWR. Clients only perform logical writes in the buffer cache

Thirdly: INSERTS may cause index blocks to be reorganized. If the index blocks aren't cached they would need to be read prior to being modified.

--
Sybrand Bakker, Senior Oracle DBA