If you enable redo log block checking, Oracle7 computes a checksum for each redo log block written to the current log. The checksums are written in the header of the block.
Oracle7 uses the checksum to detect corruption in a redo log block. Oracle7 tries to verify the redo log block when it writes the block to an archive log file and when the block is read from an archived log during recovery.
If Oracle7 detects a corruption in a redo log block while trying to archive it, Oracle7 tries to read the block from another member in the group. If the block is corrupted in all members the redo log group, then archiving cannot proceed.
See Also: For information about archiving redo log files, see Chapter 22.