Re: REDO log shifts are blocking for DB updates !!!

In article <3300699E.3C39_at_nera.no>, krc_at_nera.no wrote:

>Hi !
>
>We are currently implementing a 'time critical' system where all
>accesses towards the DB must be guaranteed a response time less or equal
>to 150 milliseconds.
>The transactions consists of both select and select for update
>statements.
>
>THE PROBLEM !!!
>Since transaction also contains updates, the REDO log file fills up and
>are switches on regular basis. During the switch the update statements
>are stalled/delayed for the same amount of time as it takes to switch
>REDO log file. Why ?????
>
>On average an update takes 25 milliseconds, but during the REDO log
>shift it is delayed for 3 SECONDS!!!!
>
>
>This has to be a 'classical' problem in 'this' database 'community' ??
>
>Are there any ways of configuring the instance (init.ora) such that LGWR
>will continue writing wile DBWR and CKPT completes there tasks during
>the REDO log shift?
>
>
>HW/SW CNFIGURATION:
>Running Oracle Server 7.3.2.2
>AlphaServer 4100 (2 CPUs), 1 GB RAM, 6 x 2.1 GB disks
>OpenVMS 7.1
>
>
>WHAT ALREADY HAS BEEN TESTED OUT!!!
>-Different sizes of REDO log files.
>-Multithreaded REDO log files.
>-The ALERT log does not contain any incomplete CHECKPOINT messages,
>indicating that CHECKPOINTS are accumulated up, until the REDO log
>shift.
>-Most init.ora parameters has been tested out. such as:
> -db_block_buffers
> -shared_pool_size,
> -log_checkpoint_interval,
> -log_checkpoint_timeout,
> -log_checkpoint_to_alert=YES,
> -db_block_checkpoint_batch,
> -db_file_simultaneous_writes,
> -log_buffers.
>
>-REDO log size has been tested out for the range 25K -> 10 MB, and we
>are currently 'stuck' on 3 MB.
>
>An attached WORD file will show the delay graphically. Both axis are in
>milliseconds.
>
>Any hints will be appreciated,
>
>
>Kjell R.

Hi
Did you try to start the Chekpoint process ????

-- 
mvh/mfg/kind regards

Niels S. Eliasen
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