Infoworld today announced that they have been researching a flaw in oracle that can result in the inability to restore your database. Large oracle shops with interconnected databases are most at risk.
The problem revolves around oracle’s SCN (system change number). The number has a limit that if exceeded, can render a database unusable, even after restoring the database. Under normal circumstances, this limit would never be reached. However, there are two ways that the limit can be reached accidentally.
- A bug in Oracle’s hot backup mechanism results in a sharp increase in the SCN number under certain conditions.
- The SCN can be increased manually, resulting in all connected databases to increase their SCN as well.
The January Oracle Critical Patch Update has a patch that resolves the hot backup problem. We recommend that this patch be applied immediately, especially if you are a large shop or use hot backups. Another fix increases the limit and and makes it less likely to reach it, but the accidental (or deliberate) modification to an SCN remains a vulnerability. Extra care should be taken with all databases that connect to any critical databases in your environment.
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