Re: RMAN or Hot Backup
Date: Fri, 10 Apr 2009 21:45:49 -0500
"Michael Austin" <maustin_at_firstdbasource.com> wrote in message news:fpSDl.26820$yr3.4280_at_nlpi068.nbdc.sbc.com...
> Bob Jones wrote:
>> "joel garry" <joel-garry_at_home.com> wrote in message
>> On Apr 9, 5:07 pm, "Bob Jones" <em..._at_me.not> wrote:
>>> "jgar the jorrible" <joel-ga..._at_home.com> wrote in >>> messagenews:879adcc1-6bdc-493e-b003-301bc58ad40a_at_x31g2000prc.googlegroups.com... >>> On Mar 27, 5:15 pm, "Bob Jones" <em..._at_me.not> wrote: >>> >>>>> So yes, it is DBA basics. I really have not done too many Hot >>>>> Backups, which is why I was asking what others opinions and experience >>>>> with both are. >>>> I have no idea why you guys keep referring to non-RMAN backup as "hot >>>> backup". That is just wrong terminology. >>> - We are referring to the copying of Oracle files while the db is >>> - running. This results in an inconsistent set of data files, which can >>> - be made consistent on recovery by the application of redo. However, >>> - if the data files are not placed into backup mode before copying, >>> - there may not be enough information in redo to make them consistent. >>> - RMAN inconsistent backups are also hot backups, but RMAN is smarter >>> - than operating system utilities and can copy the blocks in the data >>> - files in a way that avoids the problems of redo, as well as avoiding >>> - suspending the system. >>> >>> I am not sure what you meant by avoiding redo problems and suspending >>> the >>> system. I see neither being a problem with non-RMAN backups. >>
>> - 1. More redo is generated. This can be an issue on a system that
>> - generates lots of redo to begin with.
>> Just make sure I hear this correctly. Non-RMAN backups cause more redo to
>> be generated?
>> - 2. It becomes common for tablespaces to be left in hot backup mode,
>> - then people ask things like "why am I generating so much redo?"
>> Still not understanding. Why would it generate more redo logs?
>> - 3. As Michael pointed out, suspend can be a problem on an unquiet
>> - system.
>> User-managed backups absolutely do not require system to be suspended. We
>> were doing backups long before RMAN even existed. Never once we had to
>> suspend the system.
> > Bob, you miss understood this... This is for a particular Storage Array > Vendor "copy" solution called a BCV (Business Continuity Volume) copy > where the database is put into hot-backup mode, alter system suspend, > split the "mirror", alter system resume, undo hot-backup mode. > > Having done these splits without the suspend mode you risk ORA-600s with > corrupted undo segments. Been there, done that.
Who said this is for your kind of backup in particular? We are talking about RMAN vs non-RMAN backup. Not using RMAN does not mean you have to suspend the system to do a backup. Received on Fri Apr 10 2009 - 21:45:49 CDT