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Re: External backup

Posted in 2009

Topics: Stored Procedures & SPL, Server Administration, Logging & Checkpoints, Versions, Editions & End-of-Life

tilleul17@web.de — — source: Usenet: comp.databases.informix

Neil Truby wrote: > IDS 10.0 for example, any O/S. > > I've never understood why we have to an onmode -c block/onmode -c unblock > when taking a clone of Informix's data disks for back-up purposes. To my > simple mind if Informix can fast recover from the original disks it should > by definition be able to recover from the clone. > > But I have it in my mind that someone here - may have been Madison - once > sent me the perfect explanation of why this is not true. But I can't find > it anywhere! > > Was it you, dear reader, and if so could you re-send it? > > Thx > Neil > > _______________________________________________ > Informix-list mailing list > Informix-list@iiug.org > http://www.iiug.org/mailman/listinfo/informix-list > Neil, I guess you mix two things up - fast recovery and a restore with a logical restore (replay of logs) If you just want to be able to get IDS online to the point in time when you take the disk split, it should be fine (although not recommended) to get the disk split without 'onmode -c block/unblock' . In this case you'd have to copy back the disk image and IDS would do a normal fast recover and get online to the last checkpoint before the disk split copy was taken. (! Assumption is that the vendor of your storage guarantees that the disk split operation is perfectly atomic). You will not be able to do a logical restore from that point. ! NB I still recommend to block IDS , even in this case ! If you want to do an extneral restore and then rollforwrd through any saved logical logs, IDS needs a constsitent checkpoint from which to start logical log restore. So in this case block and unblock is a MUST. HTH Tilman #include <disclaimer.h>

↪ replying to tilleul17@web.de
Neil Truby — — source: Usenet: comp.databases.informix

<tilleul17@web.de> wrote in message news:mailman.198.1248949897.4791.informix-list@iiug.org... > I guess you mix two things up - fast recovery and a restore with a logical > restore (replay of logs) > > If you just want to be able to get IDS online to the point in time when > you take the disk split, it should be fine (although not recommended) to > get the disk split without 'onmode -c block/unblock' . > In this case you'd have to copy back the disk image and IDS would do a > normal fast recover and get online to the last checkpoint before the disk > split copy was taken. (! Assumption is that the vendor of your storage > guarantees that the disk split operation is perfectly atomic). > You will not be able to do a logical restore from that point. > ! NB I still recommend to block IDS , even in this case ! > > If you want to do an extneral restore and then rollforwrd through any > saved logical logs, IDS needs a constsitent checkpoint from which to start > logical log restore. So in this case block and unblock is a MUST. Yes, you are exactly right, I have been confusing fast recovery and external recovery, and I had come to realise that myself! Thank you, Tilman, and amongst others Madison, Art, Marco, Dave Williams and even Obnoxio who have variously mailed me to make this clear.

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