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RE: Zero DataLoss

From: Clay Jackson <"Clay>
Date: Wed, 9 Nov 2022 15:04:06 +0000
Message-ID: <CO1PR19MB49841244BBEF94CA2176C8CC9B3E9_at_CO1PR19MB4984.namprd19.prod.outlook.com> 








As usual, MWF hit the relevant points, except perhaps not standing in the predicted meteor impact zone😊.    Also consider these points:
For ANY zero data loss system it’s possible to come up with a scenario where (committed) data will be lost.
Attempting to achieve zero data loss can be an infinite resource (time and money) sink, so one should ALWAYS consider things like the cost and probability of that “last bit” of data actually being “lost”.



And something to think about with MAA – all MAA or any “two-phase commit” system does is prevent a transaction from committing until there are multiple (presumably at least one of would be “secure”) copies of said transaction.  In a failure scenario, what really happens is that the “last transaction”, which in fact MAY have been “commitable” in a non-MAA environment, doesn’t get committed, and, like any other “in-flight” transaction, is “lost”.  All you’re really doing is changing the timing.



Good luck!



Clay Jackson






From: oracle-l-bounce_at_freelists.org <oracle-l-bounce_at_freelists.org> On Behalf Of Mark W. Farnham
Sent: Wednesday, November 9, 2022 5:27 AM
To: chrishna0007_at_gmail.com; 'Oracle L' <oracle-l_at_freelists.org>
Subject: RE: Zero DataLoss



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Presuming you’re already doing some sort of log application to a recovery system, a radio accessible way to pull the redo logs from a “dead” data center to be taken to your remote recovery site is probably the best you can do. Axxana Inc had this sort of hardware, but I’m getting a problem trying to visit their website to copy a link to you.



IF a given “disaster” has a little warning you can update a custom table (say insert a row with the current scn and timestamp), commit, alter system switch logfile, alter system archive log all to accelerate shoving all the transactions committed so far to your recovery system. You can also have a policy that switches the database to restricted in the event of a disaster “early warning” but notice that in our mostly hacked world that is a slippery slope under time pressure for analysis. In combination those steps maximize the chances of shoving the required redo logs to your remote recovery systems in time. In lieu of the overhead of MAA or a piece of hardware that has a plex of your logfiles and archived logfiles and can transmit them in a burned up building that is buried in the crevasse of an earthquake and flooded in the crevasse, that’s about as close to zero as you are going to get. (I didn’t mention nuclear, because if you put a radio transmit unit in an EMP cage, you probably interfere with its ability to transmit. I leave that as an exercise for the community.)



mwf



From: oracle-l-bounce_at_freelists.org<mailto:oracle-l-bounce_at_freelists.org> [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Krishnaprasad Yadav
Sent: Tuesday, November 08, 2022 10:55 PM
To: Oracle L


Subject: Zero DataLoss



Dear Experts,



We want to achieve zero data loss availability in our environment , for this we are planning to put MAA in DB , but we see there is overhead of redo causing lgwr events  .
so we put it back to maximum performance .



Apart from using ZDLRA  and MAA, is their any other solution we can use to achieve this? .



Regards,


Krishna





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Received on Wed Nov 09 2022 - 16:04:06 CET












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