Flashback Database is implemented using a type of log file called Flashback Database logs. The
Oracle database periodically logs before images of data blocks in the Flashback Database logs.
Block images can be reused to quickly back out the data file changes to any time at which
flashback logs were captured just before the desired target time. Then, changes from the redo log
files are applied to fill in the gap. The Flashback Database logs are automatically created and
managed in the flash recovery area.
oracle说flashback log的内容记录的是before images of data blocks，所以直观的感觉到flashback logfile的大小应该是block大小的证书倍，验证了一下确实是8k的整数倍
SQL> show parameter db_block_size
NAME TYPE VALUE
------------------------------------ ----------- --------------------
db_block_size integer 8192
SQL>
SQL> select bytes/8192 from v$flashback_database_logfile;
BYTES/8192
----------
1000
681
SQL>
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