ORACLE RMAN 高级话题一(分片与压缩)

关于maxsize 和 section size

我想在备份的时候限制文件的大小，如下：

RMAN> backup tablespace users maxsetsize 1024m;Starting backup at 11-AUG-17using channel ORA_DISK_1using channel ORA_DISK_2using channel ORA_DISK_3using channel ORA_DISK_4using channel ORA_DISK_5using channel ORA_DISK_6RMAN-00571: ===========================================================RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============RMAN-00571: ===========================================================RMAN-03002: failure of backup command at 08/11/2017 10:21:38RMAN-06183: datafile or datafile copy /u01/app/oracle/oradata/orcl/users01.dbf (file number 4) larger than MAXSETSIZE

在这里我备份的文件大小超过maxsize，所以报错了。

RMAN> backup section size 500m tablespace users;Starting backup at 11-AUG-17using channel ORA_DISK_1using channel ORA_DISK_2using channel ORA_DISK_3using channel ORA_DISK_4using channel ORA_DISK_5using channel ORA_DISK_6channel ORA_DISK_1: starting full datafile backup setchannel ORA_DISK_1: specifying datafile(s) in backup setinput datafile file number=00004 name=/u01/app/oracle/oradata/orcl/users01.dbfbacking up blocks 1 through 64000channel ORA_DISK_1: starting piece 1 at 11-AUG-17channel ORA_DISK_2: starting full datafile backup setchannel ORA_DISK_2: specifying datafile(s) in backup setinput datafile file number=00004 ×××× ×××××（中间有省略）name=/u01/app/oracle/oradata/orcl/users01.dbfbacking up blocks 320001 through 384000channel ORA_DISK_6: starting piece 6 at 11-AUG-17channel ORA_DISK_1: finished piece 1 at 11-AUG-17piece handle=/u02/backup/ORCL/backupset/2017_08_11/o1_mf_nnndf_TAG20170811T102414_drt5bgz1_.bkp tag=TAG20170811T102414 comment=NONEchannel ORA_DISK_1: backup set complete, elapsed time: 00:00:01channel ORA_DISK_1: starting full datafile backup setchannel ORA_DISK_1: specifying datafile(s) in backup setinput datafile file number=00004 name=/u01/app/oracle/oradata/orcl/users01.dbfbacking up blocks 384001 through 398240channel ORA_DISK_1: starting piece 7 at 11-AUG-17channel ORA_DISK_2: finished piece 2 at 11-AUG-17piece handle=/u02/backup/ORCL/backupset/2017_08_11/o1_mf_nnndf_TAG20170811T102414_drt5bhfy_.bkp tag=TAG20170811T102414 comment=NONEchannel ORA_DISK_2: backup set complete, elapsed time: 00:00:00channel ORA_DISK_3: finished piece 3 at 11-AUG-17piece handle=/u02/backup/ORCL/backupset/2017_08_11/o1_mf_nnndf_TAG20170811T102414_drt5bhhh_.bkp tag=TAG20170811T102414 comment=NONEchannel ORA_DISK_3: backup set complete, elapsed time: 00:00:00channel ORA_DISK_4: finished piece 4 at 11-AUG-17piece handle=/u02/backup/ORCL/backupset/2017_08_11/o1_mf_nnndf_TAG20170811T102414_drt5bhjr_.bkp tag=TAG20170811T102414 comment=NONE×××　×××　（中间有省略）handle=/u02/backup/ORCL/backupset/2017_08_11/o1_mf_nnndf_TAG20170811T102414_drt5bhmm_.bkp tag=TAG20170811T102414 comment=NONEchannel ORA_DISK_6: backup set complete, elapsed time: 00:00:00Finished backup at 11-AUG-17Starting Control File and SPFILE Autobackup at 11-AUG-17piece handle=/u02/backup/ORCL/autobackup/2017_08_11/o1_mf_s_951733455_drt5bhyq_.bkp comment=NONEFinished Control File and SPFILE Autobackup at 11-AUG-17RMAN> 我想这样达成了限制文件大小的目地[oracle@hdp 2017_08_11]$ ll -htotal 43M-rw-r-----. 1 oracle oinstall  38M Aug 11 10:24 o1_mf_nnndf_TAG20170811T102414_drt5bgz1_.bkp-rw-r-----. 1 oracle oinstall 5.1M Aug 11 10:24 o1_mf_nnndf_TAG20170811T102414_drt5bhfy_.bkp-rw-r-----. 1 oracle oinstall  40K Aug 11 10:24 o1_mf_nnndf_TAG20170811T102414_drt5bhhh_.bkp-rw-r-----. 1 oracle oinstall  40K Aug 11 10:24 o1_mf_nnndf_TAG20170811T102414_drt5bhjr_.bkp-rw-r-----. 1 oracle oinstall  40K Aug 11 10:24 o1_mf_nnndf_TAG20170811T102414_drt5bhl8_.bkp-rw-r-----. 1 oracle oinstall  40K Aug 11 10:24 o1_mf_nnndf_TAG20170811T102414_drt5bhmm_.bkp-rw-r-----. 1 oracle oinstall  56K Aug 11 10:24 o1_mf_nnndf_TAG20170811T102414_drt5bhqg_.bkp-rw-r--r--. 1 oracle oinstall  369 Aug 11 08:28 rman.sh

rman 的默认压缩方式：

CONFIGURE COMPRESSION ALGORITHM ‘BASIC’ AS OF RELEASE ‘DEFAULT’
OPTIMIZE FOR LOAD TRUE ; # default

我们用默认压缩算法：

RMAN> backup as compressed backupset database ;

drwxr-x---. 2 oracle oinstall 4096 Aug 11 11:01 2017_08_11[oracle@hdp backupset]$ du -sh *285M    2017_08_11

这里修改默认的压缩算法

RMAN> CONFIGURE COMPRESSION ALGORITHM 'medium' AS OF RELEASE 'DEFAULT'2> ;using target database control file instead of recovery catalognew RMAN configuration parameters:CONFIGURE COMPRESSION ALGORITHM 'medium' AS OF RELEASE 'DEFAULT' OPTIMIZE FOR LOAD TRUE;new RMAN configuration parameters are successfully storedRMAN> 

再次更改为最高等级的算法

RMAN> CONFIGURE COMPRESSION ALGORITHM 'HIGH' AS OF RELEASE 'DEFAULT' OPTIMIZE FOR LOAD TRUE;

测试了一下三种压缩算法的结果：

[oracle@hdp backupset]$ du -sh *278M    2017_08_11.basic229M    2017_08_11.high308M    2017_08_11.medium

结果是high级别压缩时最狠的，其次是基本压缩，当然压缩比率越大，越耗CPU。所以不要在系统繁忙阶段进行备份。

监控一下cpu的运行状况[oracle@hdp backupset]$ mpstat 2 Linux 2.6.32-358.el6.x86_64 (hdp.oracle.com)    08/11/2017  _x86_64_    (4 CPU)11:25:35 AM  CPU    %usr   %nice    %sys %iowait    %irq   %soft  %steal  %guest   %idle11:25:37 AM  all   49.50    0.00    0.38    0.00    0.00    0.00    0.00    0.00   50.1311:25:39 AM  all   49.87    0.00    0.89    0.00    0.00    0.89    0.00    0.00   48.3511:25:41 AM  all   49.31    0.00    0.50    0.00    0.00    0.00    0.00    0.00   50.1911:25:43 AM  all   49.68    0.00    0.13    0.00    0.00    0.13    0.00    0.00   50.0611:25:45 AM  all   49.87    0.00    0.25    0.00    0.00    0.00    0.00    0.00   49.87