2012-11-16 - 11-17 11gR2 "Backup and Recovery User's Guide" page 121 - 150

 

Enabling Lost Write Detection -- 写丢失探测
You can set the DB_LOST_WRITE_PROTECT initialization parameter to TYPICAL or
FULL so that a database records buffer cache block reads in the redo log. The default
setting is NONE. When the parameter is set to TYPICAL, the instance logs buffer cache
reads for read/write tablespaces in the redo log, but not read-only tablespaces. When
set to FULL, the instance also records reads for read-only tablespaces. The performance
overhead for TYPICAL mode is approximately 5 to 10% and potentially higher for
FULL mode.
-- 分为FULL,TYPICAL,NONE。通过设置这个参数，你可以知道在何时LOST，并以此为依据进行恢复。

Guaranteed Restore Points -- 保证FLASHBACK DATABASE一定恢复到的POINTS
A guaranteed restore point ensures that you can use Flashback Database to rewind a
database to its state at the restore point SCN, even if the generation of flashback logs
is disabled. If flashback logging is enabled, then a guaranteed restore point enforces
the retention of flashback logs required for Flashback Database to any SCN after the
earliest guaranteed restore point. Thus, if flashback logging is enabled, you can rewind
the database to any SCN in the continuum rather than to a single SCN only.
-- 就算把FLASHBACK功能关掉，它也能恢复到那个时间点

Assume that your primary goal is the ability to return your database to the time at
which the guaranteed restore point was created. In this case, it is usually more efficient
to turn off flashback logging and use only guaranteed restore points. For example,
suppose that you are performing an application upgrade on a database host over a
weekend. You could create a guaranteed restore point at the start of the upgrade. If the
upgrade fails, then reverse the changes with the FLASHBACK DATABASE command.
-- 这段话我觉得很好，你可以只选择使用RESTORE POINTS而关掉闪回数据库的功能，比如升级的时候使用RESTORE，可以回退。

Online Backups and Backup Mode
Unlike user-managed tools, RMAN does not require extra logging or backup mode
because it knows the format of data blocks. RMAN is guaranteed not to back up
fractured blocks. During an RMAN backup, a database server session reads each data
block and checks whether it is fractured by comparing the block header and footer. If a
block is fractured, then the session rereads the block. If the same fracture is found, then
the block is considered permanently corrupt. Also, RMAN does not need to freeze the
datafile header checkpoint because it knows the order in which the blocks are read,
which enables it to capture a known good checkpoint for the file.
-- RMAN热备与手工热备的不同，RMAN不需要FREEZE数据文件头，不需要记录额外的日志。