Flashback Technology is a new concept introduced in version 10g. In 9i, oracle has introduced a primitive version of flashback concept by introducing a package i.e "dbms_flashback".
Various technologies that are included under flashback technology are :
1.flashback database(for DBA's)
2.flashback table(for DBA's)
3.flashback transaction query(for developers)
4.flashback version query(for developers)
5.flashback data archive/total recall
In order to configure flashback database, we need to configure flash recovery area by setting the following parameters :
1.db_recovery_file_dest
2.db_recovery_file_dest_size
Once we create flash recovery area. the following files will be created in FRA :
1.archivelogs
2.multiplexed controlfiles & redolog files
3.RMAN backup sets
4.flashback logs
In oracle11g, oracle calls Flashback recovery area as fast recovery area. Once we configure flashback database, RVWR(Recovery Writer) gets enabled.
The retension of the flashback logs depends on the parameter
db_flashback_retension_target(default value 24 hours)
We need to set a value based on how long we want to flashback the database.
Archivelogs are meant to roll forward and flashback logs are meant to roll backward. With the help of flashback database we can totally eliminate the concept like point-in-time recovery.
If the number of archives that are generated are more, roll forward takes lot of time.
if the database size is 100gb, allocate atleast 150 to 200gb for FRA. As a DBA, continuously we need to monitor for the availability of space in FRA.
