restore point分为normal restorepoint 和 guaranteed restore point两种。normal restore point 仅仅作为scn和时间点的别名使用，无其他用途，占用的控制文件空间也非常小，通常无需特别关注。控制文件会自动清除normal restore point 的信息，清除时遵循如下规则：
(1) The most recent 2048 restorepoints are always kept in the control file, regardless of their age.
(2) Any restore point more recentthan the value of CONTROL_FILE_RECORD_KEEP_TIME is retained,regardless of how many restore points are defined.
guaranteed restore point 同样作为scn和时间点的别名使用，但是控制文件不会自动清除guaranteed restore point ,必须通过手工才可以删除。另外，在不开启flashback database的情况下，guaranteed restore point仍然可以使我们使用flashback database技术，只是此时我们只可以闪回到guaranteed restore point指定的时间点。此时，仍然会生出闪回日志，只是闪回日志中仅仅存储guaranteed restore point时间点之后数据块第一次发生改变时的“before image”。
我们知道，flashback database 与nologging的支持不太好，可能会造成坏块（间歇性的保持数据块前镜像，需要使用redo恢复数据）。但是在没有启用flashback database情况下的guaranteed restore point可以很好的支持nologging,因为此时不需要使用redo日志数据。在启用flashback database log的情况下，如果创建guaranteed restore point，可以保证在guaranteed restore point到当前时间的任意时间点数据库都是可以闪回的。If you enableFlashback Database and define one or more guaranteed restore points, then thedatabase performs normal flashback logging.
flashback database 可以针对某表空间关闭，如：
SQL> alter database flashback on;
Database altered.
SQL> alter tablespace users flashback off;
Tablespace altered.
SQL> create table test1 tablespace users as select * from test;
Table created.
SQL> insert into test values(1,1);
1 row created.
SQL> commit;
Commit complete.
SQL> insert into test1 select * from test;
1 row created.
SQL> commit;
Commit complete.
SQL> select current_scn from v$database;
CURRENT_SCN
-----------
1188094
SQL> insert into test select * from test;
1 row created.
SQL> commit;
Commit complete.
SQL> insert into test1 select * from test1;
1 row created.
SQL> commit;
Commit complete.
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.
Total System Global Area 267227136 bytes
Fixed Size 2227504 bytes
Variable Size 192938704 bytes
Database Buffers 67108864 bytes
Redo Buffers 4952064 bytes
Database mounted.
SQL> flashback database to scn
2 1188094;
flashback database to scn
*
ERROR at line 1:
ORA-38753: Cannot flashback data file 4; no flashback log data.
ORA-01110: data file 4: '/u01/app/oraele/oradata/orcl/users01.dbf'
SQL> alter tablespace users offline;
alter tablespace users offline
*
ERROR at line 1:
ORA-01109: database not open
SQL> alter tablespace users read only;
alter tablespace users read only
*
ERROR at line 1:
ORA-01109: database not open
SQL> alter database open;
Database altered.
SQL> alter tablespace users offline;
Tablespace altered.
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.
Total System Global Area 267227136 bytes
Fixed Size 2227504 bytes
Variable Size 192938704 bytes
Database Buffers 67108864 bytes
Redo Buffers 4952064 bytes
Database mounted.
SQL> flashback database to scn 1188094;
Flashback complete.
SQL> alter database open resetlogs;
Database altered.
SQL> alter tablespace users online;
alter tablespace users online
*
ERROR at line 1:
ORA-01190: control file or data file 4 is from before the last RESETLOGS
ORA-01110: data file 4: '/u01/app/oraele/oradata