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MAXPIECESIZE理解

原创 Linux操作系统 作者:wenhual43 时间:2013-11-20 10:02:14 0 删除 编辑
测试:maxpiecesize=5M
RMAN>
 Configure channel device type disk maxpiecesize=5M
RMAN> backup tablespace lwh ;

Starting backup at 20-NOV-13
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=10 device type=DISK
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00005 name=D:\APP\ORADATA\ORCL\LWH.DBF
input datafile file number=00006 name=D:\APP\ORADATA\ORCL\LWH01.DBF
channel ORA_DISK_1: starting piece 1 at 20-NOV-13
channel ORA_DISK_1: finished piece 1 at 20-NOV-13
piece handle=D:\APP\PRODUCT\11.2.0\DBHOME_1\DATABASE\0DOPE1QS_1_1 tag=TAG2013112
0T095644 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 20-NOV-13

测试:maxpiecesize=1M
RMAN> Configure channel device type disk maxpiecesize=1M
RMAN> backup tablespace lwh ;


Starting backup at 20-NOV-13
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=10 device type=DISK
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00005 name=D:\APP\ORADATA\ORCL\LWH.DBF
input datafile file number=00006 name=D:\APP\ORADATA\ORCL\LWH01.DBF
channel ORA_DISK_1: starting piece 1 at 20-NOV-13
channel ORA_DISK_1: finished piece 1 at 20-NOV-13
piece handle=D:\APP\PRODUCT\11.2.0\DBHOME_1\DATABASE\0COPE19O_1_1 tag=TAG2013112
0T094735 comment=NONE
channel ORA_DISK_1: starting piece 2 at 20-NOV-13
channel ORA_DISK_1: finished piece 2 at 20-NOV-13
piece handle=D:\APP\PRODUCT\11.2.0\DBHOME_1\DATABASE\0COPE19O_2_1 tag=TAG2013112
0T094735 comment=NONE
channel ORA_DISK_1: starting piece 3 at 20-NOV-13
channel ORA_DISK_1: finished piece 3 at 20-NOV-13
piece handle=D:\APP\PRODUCT\11.2.0\DBHOME_1\DATABASE\0COPE19O_3_1 tag=TAG2013112
0T094735 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:03
Finished backup at 20-NOV-13

结论:
表空间lwh= 40M,由2个20m的数据文件构成。配置maxpiecesize=5M,为什么备份后,只有一个文件?
原因:生成的备份只有2.3m,当然就不会生成多个文件了。不要想当然的认为会生成8个文件哦!备份集是会
跳过空块,只备份有数据的块,所以备份集会比数据文件小很多!当配置maxpiecesize=1M,备份集有2.3M,就拆成了3个小piece,它们同属于一个备份集。

来自 “ ITPUB博客 ” ,链接:http://blog.itpub.net/25027760/viewspace-777053/,如需转载,请注明出处,否则将追究法律责任。

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