Re: External backup/restore - an idea - comments please

Thanks for the comments. > There's a caveat: > Transactions that are open at backup/archive time > can mean that at restore they need to be rolled back. > (That happens if they cannot be rolled forward until > commit - for whatever reason.) > That in turn means that ON-Bar will need to restore > those logs if you backed up and restore with ON-Bar. > Therefore it is possible, that you need to restore > logical logs that became full and were backed up > well before the actual dbspaces were backed up > with ON-Bar. This was the catch I was looking for. Now I know it's not only logs taken after (non-whole-system) backup that count in case of restore. Whole system backup could be the solution because our database is quite small (just few gigabytes) but I wanted to have a broader solution. > One possible solution: > For the external backup and restore you do not > really need logical log backup and restore. > This is because open transaction log records are > all still contained on disk (think of long transaction > abort scenarios because of this rule). Therefore > when you externally backup all chunks, this will > conatin those logs on disk. With that the external > restore will also restore those logs and if rollback > of open transaction is necessary, it can be done > without (extra) log restore. I'm glad you pointed this out. It's so obvious that logical logs also get externally backed up, but I completely forgot about it. All the time I was thinking how to get them from their chunks into filesystem. > With version 10.00 you can do the external restore > using the appropriate ontape command for > physical external restore ("ontape -p -e"). After that > you can do a "logical restore" ("ontape -l"), but > you do not really provide a proper tape. Instead > you say you have no more tapes and it will then > bring the server to online mode (if necessary using > the logs on disk already restored externally). I tried something like like this yesterday after posting an initial idea. The difference was that I dumped logical logs to filesystem with ontape -a (and LTAPEDEV with something like /usr/informix/logs/log) and used them for logical restore (ontape -l) after I copied chunks back and did the external restore (ontape -p -e). It went fine. One thing I didn't know is I don't really have to provide logs for "ontape -l" (I never used ontape before, onbar worked great from the first day). > That way you can backup all logs using ON-Bar. > And you don't need logs for external restore. Perfectly! I'll try this solution and report the results. Also, thanks for the links to articles. > You can read more about that in a developerWorks > article that I wrote some time ago: > > http://www.ibm.com/developerworks/db2/library/techarticle/dm-0503fuerderer/ > Or look at this article (shorter and not by me): > http://www.ibm.com/support/docview.wss?uid=swg21203380