2010年（61）
分类： Oracle
2010-02-23 09:47:31
版本的RMAN中的BACKUP命令新增了一个AS COMPRESSED BACKUPSET的选项。如果在执行BACKUP命令时指定了该选项，备份集在创建过程中就会应用压缩算法，通过这种方式使用倒是挺简单的，也不需要其他额外的操作。例如：
RMAN> BACKUP AS COMPRESSED BACKUPSET TABLESPACE SYSTEM;
Starting backup at 15-APR-09
using channel ORA_DISK_1
channel ORA_DISK_1: starting compressed full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
input datafile fno=00001 name=F:\ORACLE\ORADATA\JSSBOOK\SYSTEM01.DBF
channel ORA_DISK_1: starting piece 1 at 15-APR-09
channel ORA_DISK_1: finished piece 1 at 15-APR-09
piece handle=F:\ORACLE\BACKUP\BAK_11KCIHRB_1_1 tag=TAG20090415T214059 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:15
channel ORA_DISK_1: starting compressed full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
including current control file in backupset
including current SPFILE in backupset
channel ORA_DISK_1: starting piece 1 at 15-APR-09
channel ORA_DISK_1: finished piece 1 at 15-APR-09
piece handle=F:\ORACLE\BACKUP\BAK_12KCIHRQ_1_1 tag=TAG20090415T214059 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:03
Finished backup at 15-APR-09接着对相同表空间创建一个不压缩的备份集：
RMAN> BACKUP TABLESPACE SYSTEM;
Starting backup at 15-APR-09
using channel ORA_DISK_1
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
input datafile fno=00001 name=F:\ORACLE\ORADATA\JSSBOOK\SYSTEM01.DBF
channel ORA_DISK_1: starting piece 1 at 15-APR-09
channel ORA_DISK_1: finished piece 1 at 15-APR-09
piece handle=F:\ORACLE\BACKUP\BAK_13KCIHS6_1_1 tag=TAG20090415T214126 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:15
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
including current control file in backupset
including current SPFILE in backupset
channel ORA_DISK_1: starting piece 1 at 15-APR-09
channel ORA_DISK_1: finished piece 1 at 15-APR-09
piece handle=F:\ORACLE\BACKUP\BAK_14KCIHSM_1_1 tag=TAG20090415T214126 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:02
Finished backup at 15-APR-09列出两个备份集，对比看看：
RMAN> LIST BACKUP OF TABLESPACE SYSTEM;
List of Backup Sets
===================
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
29 Full 27.60M DISK 00:00:09 15-APR-09
BP Key: 96 Status: AVAILABLE Compressed: YES Tag: TAG20090415T214059
Piece Name: F:\ORACLE\BACKUP\BAK_11KCIHRB_1_1
List of Datafiles in backup set 29
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
1 Full 798005 15-APR-09 F:\ORACLE\ORADATA\JSSBOOK\SYSTEM01.DBF
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
31 Full 129.20M DISK 00:00:13 15-APR-09
BP Key: 98 Status: AVAILABLE Compressed: NO Tag: TAG20090415T214126
Piece Name: F:\ORACLE\BACKUP\BAK_13KCIHS6_1_1
List of Datafiles in backup set 31
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
1 Full 798020 15-APR-09 F:\ORACLE\ORADATA\JSSBOOK\SYSTEM01.DBF从LIST BACKUP中的信息可以看出，压缩比还是比较理想。不过压缩备份集虽然能够节省一些存储空间，但肯定会降低备份和恢复时的速度，这中间如何取舍就取决于你的实际需求了。
提示：
这里显示创建不压缩的备份集反而费时更长，这是因为我们库较小，因此压缩所花费的时间，相比压缩后由于备份集缩小而节省出的写磁盘时间更短，更多的时间都是花在I/O而不是压缩备份集，因此不压缩的备份集花费时间更长了。从10g R2版本开始，RMAN支持对备份集进行加密，括弧，俺说的是备份集哟，RMAN中创建的镜像复制并不支持加密。
对备份集进行加密主要是为了保护备份集的安全，启用了加密措施后，创建的备份集在恢复时也必须要有相应的密钥才能够进行恢复。
RMAN 提供三种加密的方式：透明模式、密码模式和双重模式。关于三种模式的特点的描述，请耐心等候，如果你很着急，想马上知道，往后翻到本章最后一节。
RMAN 提供了两种方式设置加密备份：
两种方式都能够启用或禁用备份加密，其中CONFIGURE命令相当于进行预定义配置，设置之后除非显式修改，否则将持续有效。SET ENCRYPTION命令则是仅作用于当前会话，不过使用上更加灵活。SET ENCRYPTION优先级比较高，如果通过CONFIGURE命令进行配置后，又执行SET ENCRYPTION命令，则SET ENCRYPTION命令指定的配置将会覆盖CONFIGURE命令的配置。
用CONFIGURE命令启用备份加密的操作非常简单（前提是端已经配置好了Oracle Encryption Wallet）：
RMAN> CONFIGURE ENCRYPTION FOR DATABASE ON;
new RMAN configuration parameters:
CONFIGURE ENCRYPTION FOR DATABASE ON;
new RMAN configuration parameters are successfully stored然后再执行备份命令创建的备份集，就是加密备份集。
如果要禁止的话将ON改为OFF即可：
RMAN> CONFIGURE ENCRYPTION FOR DATABASE OFF;
old RMAN configuration parameters:
CONFIGURE ENCRYPTION FOR DATABASE ON;
new RMAN configuration parameters:
CONFIGURE ENCRYPTION FOR DATABASE OFF;
new RMAN configuration parameters are successfully storedCONFIGURE 命令不仅可以指定DATABASE级，还可以具体到表空间，例如：
RMAN> CONFIGURE ENCRYPTION FOR TABLESPACE USERS ON ;
tablespace USERS will be encrypted in future backup sets
new RMAN configuration parameters are successfully stored使用SET ENCRYPTION命令就灵活多了，随时随地都可以：
RMAN> SET ENCRYPTION ON IDENTIFIED BY encbak ONLY;
executing command: SET encryption上述命令设置了一个名为encbak的密钥（这也正是传说中的密码模式），紧接其后创建的备份集在进行恢复时，就必须使用该密钥才能够进行正常的恢复操作。
