Understanding Flashback Technology - OCP: Oracle Database 12c Administrator Certified Professional - page 388

3 oldest_flashback_time,
4 retention_target,
5 estimated_flashback_size
6 from v$flashback_database_log;
OLDEST_FLASH_SCN OLDEST_FLASH_TIME RET_TARGET EST_FLASHBACK_SIZE
---------------- ----------------- ---------- ------------------
979720 20-JUL-13 4320 298967040
SQL>
The V$FLASHBACK_DATABASE_STAT view is used to monitor the overhead of maintaining
the data in the Flashback Database logs. This view allows you to make estimates regarding
future Flashback Database operations. This is done by coming up with an estimate about
potential required space.
Let's look at the V$FLASHBACK_DATABASE_STAT view:
SQL> select * from v$flashback_database_stat;
BEGIN_TIM END_TIME FLASHBACK_DATA DB_DATA REDO_DATA
--------- --------- -------------- ---------- ----------
ESTIMATED_FLASHBACK_SIZE CON_ID
------------------------
20-JUL-13 20-JUL-13 61784064 35880960 99203072
0 3
SQL>
As you can see, the V$FLASHBACK_DATABASE_STAT dynamic view shows the utilization of
the Flashback Database log. This is determined by the begin and end times.
Performing Flashback Database Operations
The Flashback Database can be used with SQL*Plus to perform recoveries. Once the database
is configured for the Flashback Database, you just need to start the database in mount mode,
and you are ready to perform a Flashback Database recovery. You also need to get either
OLDEST_FLASHBACK_SCN or OLDEST_FLASHBACK_TIME from the V$FLASHBACK_DATABASE_LOG
view. This will allow you to utilize the TO SCN or TO TIME clause in the FLASHBACK DATABASE
clause. If you have established a restore point , you can recover to it if it is newer than the
OLDEST_FLASHBACK_SCN .
Let's walk through performing a Flashback Database recovery to an SCN:
1. First, query the V$FLASHBACK_DATABASE_LOG view to retrieve the OLDEST_FLASHBACK_SCN :
SQL> select oldest_flashback_scn, oldest_flashback_time
2 from v$flashback_database_log;