Exadata offload incremental backup

Maclean Liu(刘相兵

网友在OTN中文官方技术论坛上提问问题：
“Exadata在rman备份时候的offloading功能需要数据库打开BCT吗？同题目，BCT=Block Change Tracking。
oracle数据库中BCT是使用文件来记录一组数据块中，修改过的数据块做个标记。
rman备份时，exadata的 offloading是如何实现的呢？”

As Maclean answered
“exadata的 offload incremental backup optimization 是基于数据块为单位， 而block change tracking通过位图维护一组block， 所以 offload incremental backup的 粒度更细化 也更智能。
With Exadata，changes are tracked at the individual oracle block level rather than at the level of a large group of blocks. This result in less I/O bandwidth being consumed for backups and faster running backups.”

在Exadata上测试offload incremantal backup，未开启block change tracking的状态下， backup incremental level 1 200GB的数据文件，仅用7秒：


RMAN> report schema;

using target database control file instead of recovery catalog
Report of database schema for database with db_unique_name DBM

List of Permanent Datafiles
===========================
File Size(MB) Tablespace           RB segs Datafile Name
---- -------- -------------------- ------- ------------------------
1    16384    SYSTEM               ***     +DATA_DM01/dbm/datafile/system.256.790880171
2    16384    SYSAUX               ***     +DATA_DM01/dbm/datafile/sysaux.257.790880183
3    16384    UNDOTBS1             ***     +DATA_DM01/dbm/datafile/undotbs1.258.790880195
4    16384    UNDOTBS2             ***     +DATA_DM01/dbm/datafile/undotbs2.260.790880213
5    1024     USERS                ***     +DATA_DM01/dbm/datafile/users.261.790880225
6    204800   TESTEXA              ***     +DATA_DM01/dbm/datafile/testexa.264.792624955

List of Temporary Files
=======================
File Size(MB) Tablespace           Maxsize(MB) Tempfile Name
---- -------- -------------------- ----------- --------------------
1    32767    TEMP                 33554431    +DATA_DM01/dbm/tempfile/temp.259.790880685

RMAN>

RMAN> backup as compressed backupset incremental level 1 tablespace testexa;

Starting backup at 05-SEP-12
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=784 instance=dbm1 device type=DISK
allocated channel: ORA_DISK_2
channel ORA_DISK_2: SID=850 instance=dbm1 device type=DISK
allocated channel: ORA_DISK_3
channel ORA_DISK_3: SID=914 instance=dbm1 device type=DISK
allocated channel: ORA_DISK_4
channel ORA_DISK_4: SID=981 instance=dbm1 device type=DISK
allocated channel: ORA_DISK_5
channel ORA_DISK_5: SID=1042 instance=dbm1 device type=DISK
allocated channel: ORA_DISK_6
channel ORA_DISK_6: SID=1109 instance=dbm1 device type=DISK
allocated channel: ORA_DISK_7
channel ORA_DISK_7: SID=1174 instance=dbm1 device type=DISK
allocated channel: ORA_DISK_8
channel ORA_DISK_8: SID=1238 instance=dbm1 device type=DISK
allocated channel: ORA_DISK_9
channel ORA_DISK_9: SID=1302 instance=dbm1 device type=DISK
allocated channel: ORA_DISK_10
channel ORA_DISK_10: SID=1369 instance=dbm1 device type=DISK
allocated channel: ORA_DISK_11
channel ORA_DISK_11: SID=1435 instance=dbm1 device type=DISK
allocated channel: ORA_DISK_12
channel ORA_DISK_12: SID=3 instance=dbm1 device type=DISK
channel ORA_DISK_1: starting compressed incremental level 1 datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00006 name=+DATA_DM01/dbm/datafile/testexa.264.792624955
channel ORA_DISK_1: starting piece 1 at 05-SEP-12
channel ORA_DISK_1: finished piece 1 at 05-SEP-12
piece handle=+RECO_DM01/dbm/backupset/2012_09_05/nnndn1_tag20120905t100651_0.499.793188411 tag=TAG20120905T100651 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:07
Finished backup at 05-SEP-12

lunar

满配的效率更客观，o(∩_∩)o 哈哈：
  List of Datafiles in backup set 146
  File LV Type Ckp SCN    Ckp Time  Name
  ---- -- ---- ---------- --------- ----
  7       Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/users.326.793131723
  23      Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/db05_data_1100.261.793134437
  35      Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/db05_data_1100.266.793134445
  47      Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/db05_data_1100.376.793134453
  59      Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/db05_data_1100.364.793134461
  71      Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/db05_data_1100.359.793134469
  83      Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/db05_data_1100.519.793134477
  95      Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/db05_data_1100.507.793134485
  107     Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/db05_data_1100.495.793134493
  119     Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/db05_data_1100.483.793134501
  131     Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/db05_data_1100.471.793134509
  143     Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/db05_data_1100.609.793134517
  155     Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/db05_data_1200.621.793134733
  167     Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/db05_data_1200.633.793134741
  179     Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/db05_data_1200.645.793134749
  189     Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/db05_data_1300.655.793134759
  201     Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/db05_index_1100.694.793137351
  213     Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/db05_index_1100.672.793137369
  225     Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/db05_index_1100.684.793137389
  231     Full 12054347897415 20-SEP-12 +DATA_DM02/db05/datafile/db05_index_1300.702.793137419

BS Key  Type LV Size       Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
147     Full    1002.40M   DISK        00:02:32     20-SEP-12      

lunar

sql 'ALTER SYSTEM ARCHIVE LOG CURRENT ';
BACKUP AS COMPRESSED BACKUPSET DATABASE FORMAT '/dbfs/my_dbfs/rmanbak/databasefiles_%d_%u_%s_%T';
BACKUP AS COMPRESSED BACKUPSET ARCHIVELOG all  FORMAT '/dbfs/my_dbfs/rmanbak/archivelogs_%d_%u_%s_%T' delete input;
BACKUP AS COMPRESSED BACKUPSET CURRENT CONTROLFILE FORMAT '/dbfs/my_dbfs/rmanbak/controlfile_%d_%u_%s_%T';
RELEASE CHANNEL 1;
RELEASE CHANNEL 2;

郁闷了，备份脚本这样的，怎么这个结果………………