RE: LOG_BUFFER

From: Mark W. Farnham <mwf_at_rsiz.com>
Date: Wed, 18 May 2016 09:43:53 -0400
Message-ID: <049b01d1b10b$528db3f0$f7a91bd0$_at_rsiz.com>

If you never come close to filling the LOG_BUFFER before a flush event, then the downside is occupying memory you never use.  

I have *not observed* Oracle performance degrade due to having a large LOG_BUFFER if there is no essential better use for the memory such as caching large frequently referenced look up tables.  

I usually safely oversize the LOG_BUFFER so that hitting the buffer one-third full is not routinely the flushing event, but I've never needed as much as you are currently using.  

Once your LOG_BUFFER is big enough so you cannot write one-third of it before the time triggered flush, I *believe* that constitutes a useful upper size limit, even if your jobs are all single commit monoliths. (There may be other useful upper size limits that are smaller, ergo the use of "a" not "the" in the phrase "a useful upper size limit.")  

*Someone let me know if that is not still at least theoretically correct.*  

So while you *might* be "wasting" some memory, I'm not aware of any other harm. I don't believe they will let you set it bigger than the program can handle.  

mwf  

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Chitale, Hemant K
Sent: Wednesday, May 18, 2016 2:02 AM
To: ram.cheruvattath_at_gmail.com; oracle-l-freelists Subject: RE: LOG_BUFFER  

What kind of storage do you write to _at_4TB/hour ? How and when do you backup and purge/delete the archivelogs.  

I've seen log buffer exceeding 1GB.    

Hemant K Chitale    

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Ram Cheruvattath
Sent: Wednesday, May 18, 2016 3:00 AM
To: oracle-l-freelists
Subject: LOG_BUFFER  

Hi  

We have a 12c database that has very high redo generation (4TB/hr). Our log_buffer is set to 1GB.  

Is there a downside to setting log_bugger this big?  

Thanks

Ram

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Received on Wed May 18 2016 - 15:43:53 CEST