| When corruption occurs in Oracle database or DBF | | | | that is required for transaction recovery. |
| file, it typically hits Oracle database block on hard drive | | | | Checksum information is a representation of the |
| or in memory. The memory damages are handled with | | | | structure of logical block. A block is good if it has |
| operating system and Oracle kernel detection | | | | standard Oracle block format. Checksum validation |
| mechanism. It isn't a perfect solution in all cases; | | | | process doesn't read actual content of the block, thus, |
| sometimes, even the good memory blocks are set as | | | | it is possible that the data inside a hard drive block is |
| corrupt. Disk corruptions are most frequent types of | | | | damaged. Setting this argument prevents those blocks |
| corruptions. The blocks are not checked after they are | | | | from being saved, which do not confirm to standard |
| written to disk, until a check is requested. Oracle | | | | block format of Oracle. If block corruption is caused by |
| follows block delivery till the block has reached the | | | | format modification, it is discovered as media error. |
| operating system, which then takes over block handling | | | | - DB_BLOCK_CHECKING=TRUE- Setting up this |
| responsibility. However, since the operating system | | | | instance argument instructs Oracle for making detailed |
| does not have knowledge about Oracle block | | | | logical block checking, before making block changes. |
| structures, it may not check the blocks intelligently. In | | | | This self-consistent block checking prevents disk and |
| such cases, database becomes inaccessible and you | | | | memory corruptions. Detailed logical block checking is |
| encounter data loss. In order to access your valuable | | | | always executed by Oracle kernel, which belongs to |
| data at this point, oracle database recovery is required. | | | | system tablespace. |
| | | | | The above methods are helpful in a number of cases |
| Oracle database offers various possibilities for | | | | in preventing database block corruption. However, if |
| defending databases against data block corruptions, | | | | you do not use them or they fail to prevent corruption, |
| which include: | | | | Oracle block corruption may occur. It causes data loss |
| - DB_BLOCK_CHECKSUM=TRUE- The main method | | | | and needs DBF Recovery to be fixed. |
| of Oracle to detect block corruption is through block | | | | You can Recover Oracle Database in a quick and |
| checksum. After block modification, database writer | | | | effective way using third-party applications. The tools |
| calculates header bytes checksum. On next reread of | | | | oracle database repair using advanced and powerful |
| the same block, it is validated. Along with regular | | | | scanning mechanisms. With non-destructive conduct |
| rollback and data blocks, database also organizes redo | | | | and simple graphical user interface, they are totally |
| log blocks. Redo log blocks contain undo information | | | | safe and easy to use. |