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archivelog mode - or not?
September 6th, 2005 by Pete
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I saw with interest Tom's post to his blog titled "Archive Log Mode" a few days ago and made a note to have a look. Whilst this post is not directly about security it has a direct bearing on the results of a successful hack. Basically Tom regales a story that he gets to hear about twice a week. Someone had emailed him and said "help, the database has crashed, it won't open, we don't have a recent backup and its not in archivelog mode.". Basically they have had it. The data has gone. If you do not plan backup strategies properly, have disaster recovery plans and test for all eventualities of failure and recovery your data is doomed. It may be that you lose the data through a software failure or a hardware failure or because of a hacker. The bottom line is that if you do not have a way to recover lost data you are doomed.
That said some sites do run without archivelog mode enabled but the big difference is that its a proper decision and they know the consequences and also know how to get all their data back. This is sometimes a solution in data warehouses.
Also don't forget that there are some tools available that can help open a corrupted database and get some data out of it. Oracle has the Data UnLoader (DUL) tool. This is a tool closely guarded jewel in Oracles crown and if you have a crashed database and no other way to get the data out then you can call Oracle in to help with this tool. There are at least a couple of private tools out there that can be used as an alternative, one of which i will tell you about in a post tomorrow.
I have just added a couple of links to my Oracle Internals page about Data UnLoader (DUL), one is a link to the user guide for DUL and another link to a post about its use and some examples.
