7.1. An Overview of Block Corruption

Block corruption or physical corruption is when a block on a physical disk becomes unreadable or inconsistent to the state that the data is unusable. Block corruption can be caused by many different sources. It is often very difficult to diagnose the actual cause of the corruption.

Block corruption can be introduced by human error though the use of software, firmware, and hardware bugs. Block corruption can also be introduced by the environment that houses your Oracle database. This usually means hardware failure, but other factors can impact the way the memory and hardware function on a system that your Oracle database is installed on.

It is generally accepted that the cause of most block corruptions is human error. Often bugs, patches, or hardware can be introduced, causing block corruption. Most often, these causes of corruption can be remedied by having good operational procedures such as making changes to hardware and software in test environments before moving the changes to the production environments. Also, using redundant hardware such as mirrored disks can protect against hardware-caused block corruption.