RMAN深入解析之--内存中的RMAN

RMAN深入解析之--内存中的RMAN

RMAN会在内存中创建一些缓冲区，然后通过这些缓冲区将数据块 写入到备份中。内存的利用与PGA(有时是SGA)的总体大小有关。

内存缓冲区分为输入缓冲区和输出缓冲区。输入缓冲区（input buffer）填充从备份文件中读取数据块；输出缓冲区（output buffer）则在执行内存对内存的写操作时填充需要备份的数据块，一旦输出缓冲区被填满，输出缓冲区的内容就会被写入到备份位置。

RMAN的内存利用

在磁盘上备份会使用PGA内存空间作为备份缓冲区，PGA内存空间从用于信道进程的内存空间中分配。如果操作系统没有配置本地异步I/O,则可以利用DBWR_IO_SLAVES参数使用I/O丛属来填充内存中的输入缓冲。如果设置DBWR_IO_SLAVES参数为任意的非零值，则RMAN会自动分配4个I/O从属来协调输入缓冲区中数据块加载。为了实现这一功能，RMAN必须利用一个共享内存区域。因此，用于磁盘备份的内存缓冲区会被推入共享池，如果存在大池，则被推入大池。如果没有使用磁带I/O从属，则会在PGA中分配用于磁带输出缓冲区的内存。

查看RMAN备份输入缓冲区的信息：

[oracle@rh7 ~]$ rman target /Recovery Manager: Release 11.2.0.1.0 - Production on Tue Jun 17 18:30:27 2014Copyright (c) 1982, 2009, Oracle and/or its affiliates.  All rights reserved.connected to target database: PROD (DBID=239333010)RMAN> backup database;Starting backup at 17-JUN-14allocated channel: ORA_DISK_1channel ORA_DISK_1: SID=43 device type=DISKchannel ORA_DISK_1: starting full datafile backup setchannel ORA_DISK_1: specifying datafile(s) in backup setinput datafile file number=00001 name=/u01/app/oracle/oradata/prod/system01.dbfinput datafile file number=00002 name=/u01/app/oracle/oradata/prod/sysaux01.dbfinput datafile file number=00005 name=/u01/app/oracle/oradata/prod/example01.dbfinput datafile file number=00003 name=/u01/app/oracle/oradata/prod/undotbs01.dbfinput datafile file number=00004 name=/u01/app/oracle/oradata/prod/users01.dbfchannel ORA_DISK_1: starting piece 1 at 17-JUN-14channel ORA_DISK_1: finished piece 1 at 17-JUN-14piece handle=/u01/app/oracle/product/11.2.0/db_1/dbs/04pb386s_1_1 tag=TAG20140617T183051 comment=NONEchannel ORA_DISK_1: backup set complete, elapsed time: 00:01:42channel ORA_DISK_1: starting full datafile backup setchannel ORA_DISK_1: specifying datafile(s) in backup setincluding current control file in backup setincluding current SPFILE in backup setchannel ORA_DISK_1: starting piece 1 at 17-JUN-14channel ORA_DISK_1: finished piece 1 at 17-JUN-14piece handle=/u01/app/oracle/product/11.2.0/db_1/dbs/05pb38a3_1_1 tag=TAG20140617T183051 comment=NONEchannel ORA_DISK_1: backup set complete, elapsed time: 00:00:01Finished backup at 17-JUN-14查看缓冲区信息：sql>select set_count,device_type,type,filename,buffer_size,buffer_count,open_time,close_time  2    from v$backup_async_io  3*   order by set_count,type,open_time,close_time SET_COUNT DEVICE_TYP TYPE      FILENAME                                 BUFFER_SIZE BUFFER_COUNT OPEN_TIME CLOSE_TIM---------- ---------- --------- ---------------------------------------- ----------- ------------ --------- ---------         4 DISK       AGGREGATE                                                    0            0 17-JUN-14 17-JUN-14         4 DISK       INPUT     /u01/app/oracle/oradata/prod/example01.d      524288            6 17-JUN-14 17-JUN-14                                bf         4 DISK       INPUT     /u01/app/oracle/oradata/prod/sysaux01.db      524288            6 17-JUN-14 17-JUN-14                                f         4 DISK       INPUT     /u01/app/oracle/oradata/prod/system01.db      524288            6 17-JUN-14                                f         4 DISK       INPUT     /u01/app/oracle/oradata/prod/users01.dbf      524288            6 17-JUN-14 17-JUN-14         4 DISK       INPUT     /u01/app/oracle/oradata/prod/undotbs01.d      524288            6 17-JUN-14 17-JUN-14                                bf         4 DISK       OUTPUT    /u01/app/oracle/product/11.2.0/db_1/dbs/     1048576            4 17-JUN-14                                04pb386s_1_17 rows selected.Elapsed: 00:00:00.0218:32:19 SYS@ prod>