I don't see the connection between 24x7x365 uptime and level-0 backups. Yeah -- you're going to use a physical standby as your first line of recovery. Nobody is going to take their retail site offline for 4 hours while you spin backup tapes. But in the event of a disaster, you are probably going to failover (immediately) to the standby and continue operations while you restore the (former) "primary" database from backups. Why would this preclude the "traditional" level-0 / level-1 backup? On Thu, Feb 12, 2015 at 10:37 AM, Mladen Gogala <dmarc-noreply@xxxxxxxxxxxxx > wrote: > On 02/12/2015 09:57 AM, Powell, Mark wrote: > >> I am not sure I agree with the following logic: "With a really big DB, >> overhead of restoring several incremental backups becomes unacceptable. I >> don't know the sizes of your databases and the SLA time specified to bring >> them back, but chances are that restoring several incremental backups will >> take significant amount of time." >> >> With a large database just restoring the files will take a large amount >> of time, perhaps rendering the time necessary to apply the incremental and >> archive log relatively insignificant in comparison. You have to apply the >> archived redo logs from the last backup to bring the database current. >> Incremental backups are actually just collections of changes and the >> applying of the incremental backup replaces applying all the logs generated >> between the full backup (level 0 in this case) and the incremental backup >> so does applying incremental backups really add much if any time to the >> total recovery process? >> > > Well, in my experience, restoring an incremental backup is not a very fast > operation. To tell the truth, I haven't done it in quite a while. I do > remember duplicate database problems in 10G, when BCT was on. The control > file of the auxiliary instance was restored from the target instance and > contained an information about the BCT file which was not restored on the > auxiliary instance. The database refused to open. The workaround was to > disable the BCT during the duplicate DB and then to re-enable it, thereby > messing up my incremental backups. > > >> My ideal would be to run full backups every night and not use incremental >> backups however if I remember right incremental backups were introduced as >> a way to reduce the time necessary to run the nightly backups. So if you >> are using incremental backups to reduce the load on the machines during >> say, nightly batch, you may not really have a choice. Then we get to those >> sites where an rman full backup takes more than 24 hours to run. >> > > And that's exactly the thing that de-duplication is supposed to address. > Of course, very large databases have corresponding hardware requirements. > The primary means of maintaining the availability is always a physical > standby, if the up-time requirements are 7x24x365, and they usually are. > > >> I think backup requirements are very site specific. >> > > Yes they are. And more complex and expensive than people realize. I see > many people abandoning tapes altogether, but I am not quite clear as to > why. There is nothing else that can store 6TB of data on a $45 piece of > medium. 6TB of EMC disk space will cost much more, even if it's Isilon or > VNX. I don't even want to discuss VMAX. Problem is that with the advent of > WWW, many more sites are being asked to remain up 7 days a week, 24 hours > per day. Long, long time ago, in a galaxy far, far away, when there was no > Amazon, book shops could have shut their systems down for the Sunday > afternoon. Do that these days, and your shop will likely go the way of the > Borders Books. Banks, news and media outlets and even mortar and click > shops like Walmart have to remain open 24 hours a day, 7 days a week, 365 > days per year. Such extreme up-time requirements which were once reserved > only for the credit card companies, huge international banks, HMO's and 911 > services are now common. And that puts a completely new set of requirements > on the backup strategy. I doubt that Google could tell internet users that > they're doing maintenance and are shutting down their systems on every > first Sunday in a month, for 1 hour. Even that would be considered far too > much. And that would still be 99% up-time. Backup and restore become > extremely expensive when it is not possible to shut the company production > database down for 12 hours per year. The classic wisdom of doing a weekly > full backup over the weekend and incremental backups in the meantime no > longer apples. > > >> >> -----Original Message----- >> From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] >> On Behalf Of Mladen Gogala >> Sent: Thursday, February 12, 2015 4:02 AM >> To: oracle-l@xxxxxxxxxxxxx >> Subject: Re: block chg tracking >> >> Comments in-line >> >> On 02/12/2015 02:58 AM, John Hallas wrote: >> >>> I find backup with de-duplication technology, like Commvault Simpana, >>> far preferable to incremental backups. >>> And yes, I do work for Commvault Systems. >>> >>> Why are the 2 not compatible Mladen? >>> >> The two are compatible, but incremental backups are a nuisance. You have >> to restore the last full backup and all incremental backups since the last >> backup. And then apply logs. A full backup with de-duplication will shrink >> your backups and reduce backup time so that the storage taken by the full >> backup will be approximately the same as the storage taken by an >> incremental backup without de-duplication. Well, not quite, the usual >> de-duplication granularity is 128k and the most frequent db_block_size is >> 8k, so there is some beef added, but the savings are significant. >> >> BCT reduces the use of CPU and disk I/O as it knows which blocks have >>> changed. Yes there is an overhead in writing that information and on >>> a massively performant system such as trading system that overhead >>> might be too much, however small it is, however on most systems it is >>> not really noticeable. The benefits when running the backups are a >>> very significant trade-off though >>> >> Well, with database sizes in tens of TB, every backup becomes too slow. >> With a really big DB, overhead of restoring several incremental backups >> becomes unacceptable. I don't know the sizes of your databases and the SLA >> time specified to bring them back, but chances are that restoring several >> incremental backups will take significant amount of time. >> Restoring a single full backup will have to be done anyway, it's only the >> question of storage and the amount of time needed to recover. These days, >> it is possible even to use SAN snapshots and copy to another storage >> cabinet using SRDF, SnapVault, HDR or something similar. That is the most >> expensive option with respect to storage but definitely the fastest to >> restore. The restore is essentially SAN snapshot revert. >> However, for larger databases incremental backups are exceedingly rare. >> If something like hurricane Sandy happens, recovery will take much >> longer if incremental backups need to be restored. At some point, it pays >> off to do only full backups, with de-duplication, despite the slightly >> larger amount of storage used. >> >> And yes, we use Commvault >>> John >>> >> I am very glad that you do. Hopefully, you like it, too. If there is >> anything I can help with, my office email is mgogala@xxxxxxxxxxxxx. Of >> course, the opinions stated on this list are mine and do not reflect the >> opinions of my employer. I am not authorized to speak or make any >> statements for my employer. That is why I use Yahoo address. >> >> >> www.jhdba.wordpress.com >>> >>> >>> >>> ______________________________________________________________________ >>> Wm Morrison Supermarkets Plc is registered in England with number >>> 358949. The registered office of the company is situated at Gain Lane, >>> Bradford, West Yorkshire BD3 7DL. This email and any attachments are >>> intended for the addressee(s) only and may be confidential. >>> >>> If you are not the intended recipient, please inform the sender by >>> replying to the email that you have received in error and then destroy the >>> email. >>> If you are not the intended recipient, you must not use, disclose, copy >>> or rely on the email or its attachments in any way. >>> >>> This email does not constitute a contract in writing for the purposes of >>> the Law of Property (Miscellaneous Provisions) Act 1989. >>> >>> Our Standard Terms and Conditions of Purchase, as may be amended from >>> time to time, apply to any contract that we enter into. The current >>> version of our Standard Terms and Conditions of Purchase is available >>> at: http://www.morrisons.co.uk/gscop >>> >>> Although we have taken steps to ensure the email and its attachments >>> are virus-free, we cannot guarantee this or accept any responsibility, >>> and it is the responsibility of recipients to carry out their own virus >>> checks. >>> ______________________________________________________________________ >>> i 0 zX + n { +i ^l=== >>> >> >> -- >> Mladen Gogala >> Oracle DBA >> http://mgogala.freehostia.com >> >> -- >> //www.freelists.org/webpage/oracle-l >> >> >> ��i��0���zX���+�� n��{�+i�^l=== >> > > > -- > Mladen Gogala > Oracle DBA > http://mgogala.freehostia.com > > -- > //www.freelists.org/webpage/oracle-l > > >