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In-depth Analysis of RMAN-- RMAN in memory

RMAN creates some buffers in memory and then writes blocks to the backup through those buffers. Memory utilization is related to the overall size of the PGA (and sometimes SGA).

The memory buffer is divided into input buffer and output buffer. The input buffer (input buffer) fills the data blocks read from the backup file, and the output buffer (output buffer) fills the data blocks that need to be backed up when writing from memory to memory. Once the output buffer is filled, the contents of the output buffer are written to the backup location.

Memory Utilization of RMAN

Backup on disk uses PGA memory space as the backup buffer, and PGA memory space is allocated from the memory space used for channel processes. If the operating system is not configured with local asynchronous IAccord O, you can use the DBWR_IO_SLAVES parameter to populate the input buffer in memory with the Imax O cluster attribute. If the DBWR_IO_SLAVES parameter is set to any non-zero value, RMAN automatically allocates four Istroke O slaves to coordinate block loading in the input buffer. To achieve this, RMAN must take advantage of a shared memory area. As a result, the memory buffer used for disk backups is pushed into the shared pool or, if there is a large pool, into the large pool. If the tape Iamp O slave is not used, the memory used for the tape output buffer is allocated in PGA.

View the information of the RMAN backup input buffer:

[oracle@rh7] $rman target / Recovery Manager: Release 11.2.0.1.0-Production on Tue Jun 17 18:30:27 2014Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved.connected to target database: PROD (DBID=239333010) RMAN > backup database Starting backup at 17-JUN-14allocated channel: ORA_DISK_1channel ORA_DISK_1: SID=43 device type=DISKchannel ORA_DISK_1: starting full datafile backup setchannel ORA_DISK_1: specifying datafile (s) in backup setinput datafile file number=00001 name=/u01/app/oracle/oradata/prod/system01.dbfinput datafile file number=00002 name=/u01/app/oracle/oradata/prod/sysaux01.dbfinput datafile file number=00005 name=/u01/app/oracle/oradata/prod/example01.dbfinput datafile file number=00003 name=/u01/app/oracle/oradata/prod/undotbs01. Dbfinput datafile file number=00004 name=/u01/app/oracle/oradata/prod/users01.dbfchannel ORA_DISK_1: starting piece 1 at 17-JUN-14channel ORA_DISK_1: finished piece 1 at 17-JUN-14piece handle=/u01/app/oracle/product/11.2.0/db_1/dbs/04pb386s_1_1 tag=TAG20140617T183051 comment=NONEchannel ORA_DISK_1: backup set complete Elapsed time: 00:01:42channel ORA_DISK_1: starting full datafile backup setchannel ORA_DISK_1: specifying datafile (s) in backup setincluding current control file in backup setincluding current SPFILE in backup setchannel ORA_DISK_1: starting piece 1 at 17-JUN-14channel ORA_DISK_1: finished piece 1 at 17-JUN-14piece handle=/u01/app/oracle/product/11.2.0/db_1/dbs/05pb38a3_1_1 tag=TAG20140617T183051 comment=NONEchannel ORA_DISK_1: backup set complete Elapsed time: 00:00:01Finished backup at 17-JUN-14 View buffer information: sql > select set_count,device_type,type,filename,buffer_size,buffer_count,open_time,close_time 2 from v$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: 0000 u01/app/oracle/product/11.2.0/db_1/dbs/ 00.021815 32 SYS@ prod >

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