Re: CHECKPOINTS

From: Steve Adams <steve.adams_at_ixora.com.au>
Date: 2000/03/02
Message-ID: <38bde49d.37255270@news.eagles.bbs.net.au>#1/1

Hi Mario,

This is a DBWn bottleneck.
Some questions ...

What version of AIX?
Is aio available (it should be)?
  To find out, do the following as root
  # smit aio
  select "Change/Show Characteristics of Asynchronous I/O" How many datafiles do you have?
How many physical disks (spindles) underlying the data files (not counting log files)?
What are the values of the following parameters?   use_async_io

  db_writers
  db_files
  db_file_simultaneous_writes

  _db_block_write_batch (if set)

  db_block_checkpoint_batch
  db_block_buffers
  db_block_size

Regards,
Steve Adams

http://www.ixora.com.au/
http://www.oreilly.com/catalog/orinternals/
http://www.christianity.net.au/

On Wed, 1 Mar 2000 23:12:32 +0100, "Mario" <mtechera_at_yahoo.com> wrote:

>
>We have a problem with redo log switching
>when running large jobs. All groups fill up
>and remain active even though they
>are archived - presumably this is because
>checkpointing is going on.
>
>Finally when the
>last log group fills and wants to switch back to
>the first group it cannot do so, because
>the first group is still active. At this point the system
>slows to a crawl and even trivial queries require minutes
>for a response.
>
>We have
>increased the number of redo log groups
>(almost doubling the space available),
>and have also increased the initialization
>parameter db_block_checkpoint_batch
>so as to allow for faster checkpointing.
>Yet the problem persists.
>
>Does anyone have any pointers for us?
>
>Is there any good documentation on how the checkpoint
>process works and why it takes so long?
>
>Our System
>Oracle V7.3.4, RS/6000, 2CPUs, 1.3 GB Memory, AIX
>
>Thanks in advance,
>Mario
>
>
>
>
Received on Thu Mar 02 2000 - 00:00:00 CST