RE: DataGuard with LGWR ASYNC or even ARCH

I understand that Maximum Performance is ASYNC. I consider that as an option to Maximum Availability with SYNC.  

ARCH can be used with ARCHIVE_LAG_TARGET so that we set time-bound archival.  

Hemant K Chitale    

From: Nassyam Basha [mailto:nassyambasha_at_gmail.com] Sent: Tuesday, September 09, 2014 12:23 PM To: Chitale, Hemant K
Cc: ORACLE-L
Subject: Re: DataGuard with LGWR ASYNC or even ARCH  

Hi Hemant,

Even any version, Maximum performance works only with ASYNC.. and SYNC is applicable only in maximum protection and availability. which decides redo data should send synchronously or asynchronously to the remote destinations.

When you say whether to use ARCH or LGWR... Oracle recommends to use LGWR transport so that you can have standby with always minimum data lag. Let's consider for example we do have 5 GB of online redo log which is dumped as archive with same size(5gb may not same, depends on switch)

1. Primary will try to send 5GB of data in bulk in case of ARCH transport...
2. If online redo log crashed when 4GB of 5GB is filled and then 4GB of data still not reached to standby then it is definitely more painful.

In case of LGWR transport, whenever redo received by RFS of standby database then RFS writes the redo into the SRL's and recovery will be performed from the data of SRL's hence you can avail minimum data loss.  

What above I've mentioned its well known to you am sure, am revising once :)

> When there are wide fluctuations in redo volume and the bandwidth is grossly inadequate for the peak volumes, I would even consider ARCH
 

Yes, it depends on how much redo size generated per second and whether bandwidth suffice or not.. In order to do that by estimating the bandwidth size/redo size we can also go with SDU allocation so that we can control even in peak hours.

Please let me know if i fail to understand your question. Thank you.    

On Tue, Sep 9, 2014 at 8:37 AM, Chitale, Hemant K <Hemant-K.Chitale_at_sc.com> wrote:

I believe that there are valid reasons for the need to use LGWR ASYNC , Maximum Performance mode, instead of Maximum Availability mode even in 11g.

When there are wide fluctuations in redo volume and the bandwidth is grossly inadequate for the peak volumes, I would even consider ARCH.

What criteria would you use to qualify a DataGuard environment to run ASYNC, Maximum Performance ?

Hemant K Chitale

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