Flashback Database logs裡的內容是什麼？

按照oracle的說法是before images of data blocks[@more@]

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說flashback log的內容記錄的是before images of data blocks，所以直觀的感覺到flashback logfile的大小應該是block大小的證照倍，驗證了一下確實是8k的整數倍

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>