Bob, Yes... For Business Continuance (HP) or SRDF (EMC) kinda solutions it is becoming an urban Legend. I will give you an example... 1.2 TB usable disk spsce by HP's XP disk solution costs us almost 800 K USD , that too after all kinds of discounts.
Like John said, considering it saves a whole lot of trouble and kinda fun to have around, it is invaluable...provided you can persuade damagement to part with that kinda money..;) Cheers, RS --- "Freeman, Robert " <[EMAIL PROTECTED]> wrote: > John, > > Yes, and I could kick myself for not thinking of > this, mirrors can be a most > excellent alternative to backups both production and > after a recovery. Of > course, it can be an expensive alternative as it > requires you to have > 2x disk space... :-) > > But disk is cheap, right...? > > Or is that yet another Urban Legend??? > > RF > > Robert G. Freeman - Oracle8i OCP > Oracle DBA Technical Lead > CSX Midtier Database Administration > > The Cigarette Smoking Man: Anyone who can appease a > man's conscience can > take his freedom away from him. > > > > -----Original Message----- > Sent: Monday, March 18, 2002 1:18 PM > To: Multiple recipients of list ORACLE-L > > > Hi all, > > Notice the renamed heading - this thread has really > taken off! > > Coming back to the issue: While I agree that you > should not open the > database until after you backup (hot or cold), I am > still rooting for a hot > backup. If you know the application well enough, you > can perform 'selective > hot backup' of a required set of tablespaces that > you know will be changed, > and continue hot backup of the others after the > database is opened up. In a > cold backup situation, the whole database is down > for backup (including > large TEMP tablespaces - 13Gb out of 130 Gb on one > of my Production Apps > databases!) for a longer duration than is necessary, > which does not look too > good on your availability reports. (And also > remember to switch logfiles so > that archivelogs are generated prior to release to > users). > > Having said all that, a soft mirror that can be used > exclusively for backup > is invaluable. The whole database can be put in > backup mode for a short > time, the mirror 'broken' and the database backup > ended. The mirror can then > be used for backup to tape. In addition to this, you > also have an online > backup available (until the resilver starts) and you > work off this disk > backup for producting clones. Let me say that again > - Invaluable! > > John Kanagaraj > Oracle Applications DBA > DBSoft Inc > (W): 408-970-7002 > > Grace - Getting something we don't deserve > Mercy - NOT getting something we deserve > > Click on 'http://www.needhim.org' for Grace and > Mercy that is freely > available! > > ** The opinions and statements above are entirely my > own and not those of my > employer or clients ** > > > > 1. You do not open the database to users until > AFTER you do a > > backup (hot or > > cold, dosen't mater) at point t2. > > > > 2. There is a method of recovering a database (8i > +) after > > RESETLOGS has > > been > > issued with archived redo logs. I discussed it in > my DBA > > > > > * You *have* to take a COLD backup of the > database after using > > > resetlogs. > > > > (Not required - a Hot backup and archive logs > is > > adequate. All hot > > > backups / > > > > archive logs prior to that are invalid, > though...) > > > > > > Consider the following: > > > > > > Time: > > > > > > t0: database restored > > > t1: database opened with RESETLOGS > > > t2: hot backup started ( database in archive log > mode ) > > > t3: users input very important transactions > > > t4: database crashes, and must be restored > > > > > > How will you recover the transactions from time > t3? > > > > As long as the online redologs are available, this > should be > > no problem. I > > have successfully recovered databases where a log > switch did > > not occur and > > recovery had to use an online redo log. (I am > assuming that the lost > > datafiles will be restored from this hot backup > fresh off the tapes) > > > > On the other hand, if the online redolog is hosed > you have lost the > > transactions anyway, _regardless_ of the fact that > a Cold > > backup was taken. > > Then you will have to go back to the _previous_ > incarnation > > and redo the > > restore and then perform a ccf/resetlogs (i.e. > back to square > > one). If you > > have a Cold backup, you restore the cold backup > and go on > > with life. I.e. in > > both cases (availability of cold or hot backup, > lost online > > redo log), you > > have lost transactions... > > > > Additionally, with a Hot backup and depending on > what was > > lost, you can at > > least perform tablespace/datafile recovery . With > a cold > > backup, you will > > have to restore the whole database.... > > > > The point I was trying to make was that a Cold > backup after a > > RESETLOGS does > > not serve anything. Maybe there is still a gotcha > I have not > > been able to > > figure out, so Backup/restore Gurus: take a bash > at this > > logic! I would love > > to be corrected. > > > > (Btw, the previous recovery scenario was on 7.3.4 > - things could have > > changed since, and I have not been able to test > that out...) > > > > > > John Kanagaraj > > Oracle Applications DBA > > DBSoft Inc > > (W): 408-970-7002 > > > > Grace - Getting something we don't deserve > > Mercy - NOT getting something we deserve > > > > Click on 'http://www.needhim.org' for Grace and > Mercy that is freely > > available! > > > > ** The opinions and statements above are entirely > my own and > > not those of my > > employer or clients ** > > > > > > -- > > Please see the official ORACLE-L FAQ: > http://www.orafaq.com > > -- > > Author: John Kanagaraj > === message truncated === __________________________________________________ Do You Yahoo!? Yahoo! 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