Flashback query is not enabled by default and must be turned on in following sequence. We will set retention to 10 hours (600 minutes), set recovery size up to 2 GB in file “/recovery/flashback”:
shutdown immediate;
startup mount;
alter database archivelog;
alter system set DB_FLASHBACK_RETENTION_TARGET=600;
alter system set DB_RECOVERY_FILE_DEST_SIZE=2G;
alter system set DB_RECOVERY_FILE_DEST=’/recovery/flashback’;
alter database flashback on;
alter database open;