Re: buffer pool

Daud wrote:

> I was reading the Oracle 8i doc on Designing and Tuning for
> Performance when I came across a section on how to set the value of
> db_block_lru_latches and db_writer_processes. My question is how do I
> know if I have multiple buffer pool (default, keep and recycle)? I
> never explicitly set it to anything in my table creation script. I
> guess I only have one (default). Am I correct? Is there a way to
> confirm this?

All pool sizes are explicit set in init.ora file, so you *must* know. db_block_buffers = 250000
db_block_lru_latches = 7
buffer_pool_keep = (buffers:50000, lru_latches:2) ... RDFM
>
> My oracle is running on a 8-cpu unix machine. By default,
> db_block_lru_latches will be set to 4. With 1 db writer, will I see
> any performance improvement at all by increasing db_block_lru_latches
> to 16 (# of cpu x 2)?

Only if you have latch contention, free buffer waits, cache buffers lru chain or other buffer related contention.

> Is there any relation between
> db_writer_processes and db_block_lru_latches?

Latches are for atomically serialization of parallel processes; critical structures are protected by latches, only one process at a time can manipulate then, or the structures would get corrupt. Db_writer is freeing buffers, hence it manipulates the LRU list.

>
> rgds
> Daud
>

If you don't have a problem, why fix it?

rgds
Svend Received on Thu Aug 01 2002 - 15:41:58 CDT