Verifying Data Blocks in Datafiles - Oracle 10g

If you want to configure the database to use checksums to verify data blocks, set the initialization parameter DB_BLOCK_CHECKSUM to TRUE. This causes the DBWn process and the direct loader to calculate a checksum for each block and to store the checksum in the block header when writing the block to disk.

The checksum is verified when the block is read, but only if DB_BLOCK_CHECKSUM is TRUE and the last write of the block stored a checksum. If corruption is detected, the database returns message ORA-01578 and writes information about the corruption to the alert file.

The default value of DB_BLOCK_CHECKSUM is TRUE. The value of this parameter can be changed dynamically using the ALTER SYSTEM statement. Regardless of the setting of this parameter, checksums are always used to verify data blocks in the SYSTEM tablespace.


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