BCT（Block Change Tracking）块变化跟踪、增量和差异备份

1. BCT
- 1.1原理
- 1.2配置方法
  - 开启
  - 关闭
2. 增量和差异备份
3. 定时脚本

1. BCT

1.1原理

BCT（Block Change Tracking）是Oracle从10g开始有的特性。BCT的原理是记录数据文件里每个数据块的变化，并把这些变化信息保存在BCT的跟踪文件中。启动BCT后，RMAN或者XTTS进行增量备份时使用BCT跟踪文件里的信息，只读取改化的数据块，而不用再对全部数据文件进行扫描，从而提高了RMAN或者XTTS增量备份的性能。

未启动快速增量备份，RMAN备份必须检查数据文件中所有块的变化（SCN），即扫描所有的数据库，导致备份慢，

启动快速增量备份，块的改变被记录在一个文件中，RMAN只需读取文件中记录的块，加快备份速度。

隐含参数：_bct_bitmaps_per_file

在启用了块更改跟踪的数据库上，如果执行了8个以上的RMAN增量备份而没有将它们合并为完整备份，BCT跟踪文件可能无法使用。这个限制由隐含参数 “_bct_bitmaps_per_file"参数决定。这个参数设置每个数据文件要存储的位图数，其默认值为8。为了避免此问题，可以运行不超过8个增量备份就进行一次全量备份，也可以增加”_bct_bitmaps_per_file"参数。

监视快跟踪

v$backup_datafile的used_change_tracking的列查看是否使用块跟踪

select * from v$backup_datafile order by file#; 

select file#,avg(datafile_blocks),avg(blocks_read),avg(blocks_read/datafile_blocks)*100 as pct_read_for_backup, avg(blocks)
                	from v$backup_datafile
              		where used_change_tracking = 'YES'
              		and incremental_level > 0 
              		group by file#;

1.2配置方法

可以通过v$block_change_tracking;查看是否开启

开启

方法一：

配置DB_CREATE_FILE_DEST，默认放在mof或中

SQL> alter system set db_create_file_dest='/opt/soft/rman';
SQL> alter database enable block change tracking;

方法二：

SQL> alter database enable block change tracking using file '/home/oracle/blk.trc';

关闭

enable改为disable

禁用后，bct file会随着禁用而自动被删除清理。

ALTER DATABASE DISABLE BLOCK CHANGE TRACKING;

2. 增量和差异备份

BCT的实施要在全量备份之前，否则增量备份时不会起作用，很多人误以为在增量备份之前即可。

0级全备

run {
allocate channel ch1 device type disk format '/tmp/test/full_0_%d_%s';
allocate channel ch2 device type disk format '/tmp/test/full_0_%d_%s';
sql'alter system switch logfile';
backup as compressed backupset incremental level 0 database plus archivelog delete input;
backup current controlfile;
crosscheck backup;
delete noprompt expired backup;
delete noprompt obsolete;
release channel ch1;
release channel ch2;
}

执行0级备份

#全备前开启BTC,否则没效果，还是会扫描全部数据文件
SQL> alter database enable block change tracking using file '/home/oracle/blk.trc';

数据库已更改。

[oracle@db1 ~]$ rman target /
RMAN>

run {
allocate channel ch1 device type disk format '/tmp/test/full_0_%d_%s';
allocate channel ch2 device type disk format '/tmp/test/full_0_%d_%s';
sql'alter system switch logfile';
backup as compressed backupset incremental level 0 database plus archivelog delete input;
backup current controlfile;
crosscheck backup;
delete noprompt expired backup;
delete noprompt obsolete;
release channel ch1;
release channel ch2;
12> }


#rman控制文件自动备份没开就要加上
#backup current controlfile; #rman控制文件自动备份没开就要加上
#report obsolete;针对的是全备，并非0级，意义不大

查看备份

RMAN> list backup of database;

List of Backup Sets
===================


BS Key  Type LV Size       Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
87      Incr 0  103.15M    DISK        00:00:19     11-MAY-22
        BP Key: 87   Status: AVAILABLE  Compressed: YES  Tag: TAG20220511T101325
        Piece Name: /tmp/test/full_0_ORCL_113
  List of Datafiles in backup set 87
  File LV Type Ckp SCN    Ckp Time  Abs Fuz SCN Sparse Name
  ---- -- ---- ---------- --------- ----------- ------ ----
  3    0  Incr 3053406    11-MAY-22              NO    /u01/app/oracle/oradata/ORCL/sysaux01.dbf
  7    0  Incr 3053406    11-MAY-22              NO    /u01/app/oracle/oradata/ORCL/users01.dbf

。。。。。。。。
例如：LV为0，类型为增量， file3,7两个备份集，备份片/tmp/test/full_0_ORCL_26

#查看归档
RMAN> list backup of archivelog all;

List of Backup Sets
===================


BS Key  Size       Device Type Elapsed Time Completion Time
------- ---------- ----------- ------------ ---------------
95      13.50K     DISK        00:00:00     11-MAY-22
        BP Key: 95   Status: AVAILABLE  Compressed: YES  Tag: TAG20220511T101441
        Piece Name: /tmp/test/full_0_ORCL_120

  List of Archived Logs in backup set 95
  Thrd Seq     Low SCN    Low Time  Next SCN   Next Time
  ---- ------- ---------- --------- ---------- ---------
  1    7       3053385    11-MAY-22 3053452    11-MAY-22

...........





#注意查看控制文件，如果开启了默认自动备份控制文件，这里将有两个备份，
#一个普通全备一个增量0级，注意大小
RMAN> list backup of controlfile;


备份集列表
===================


BS 关键字  类型 LV 大小       设备类型 经过时间 完成时间
------- ---- -- ---------- ----------- ------------ ----------
27      Incr 0  1.05M      DISK        00:00:01     10-5月 -22
        BP 关键字: 27   状态: AVAILABLE  已压缩: YES  标记: TAG20220510T213057
段名:/tmp/test/full_0_ORCL_31
  包括的控制文件: Ckp SCN: 3250543      Ckp 时间: 10-5月 -22

BS 关键字  类型 LV 大小       设备类型 经过时间 完成时间
------- ---- -- ---------- ----------- ------------ ----------
30      Full    17.95M     DISK        00:00:00     10-5月 -22
        BP 关键字: 30   状态: AVAILABLE  已压缩: NO  标记: TAG20220510T213136
段名:/u01/app/oracle/product/19.3/dbhome_1/dbs/c-1631360725-20220510-00
  包括的控制文件: Ckp SCN: 3250717      Ckp 时间: 10-5月 -22

#如果关闭，则一个正常的全备，说明自动备份控制文件后增量
RMAN> list backup of controlfile;


List of Backup Sets
===================


BS Key  Type LV Size       Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
96      Full    18.23M     DISK        00:00:03     11-MAY-22
        BP Key: 96   Status: AVAILABLE  Compressed: NO  Tag: TAG20220511T101443
        Piece Name: /tmp/test/full_0_ORCL_121
  Control File Included: Ckp SCN: 3053472      Ckp time: 11-MAY-22

差异增量

与上一次0级全备或1级差异的差异,默认方式

run {
allocate channel ch1 device type disk format '/tmp/test/full_0_%d_%s';
allocate channel ch2 device type disk format '/tmp/test/full_0_%d_%s';
sql'alter system switch logfile';
backup as compressed backupset incremental level 1 database plus archivelog delete input;
backup current controlfile;
crosscheck backup;
delete noprompt expired backup;
delete noprompt obsolete;
release channel ch1;
release channel ch2;
}

累积增量

累积增量是指备份自上次0级备份以来所有发生变化的数据块，忽略之前的1级备份。

run {
allocate channel ch1 device type disk format '/tmp/test/full_0_%d_%s';
allocate channel ch2 device type disk format '/tmp/test/full_0_%d_%s';
sql'alter system switch logfile';
backup as compressed backupset incremental level 1 cumulative database plus archivelog delete input;
backup current controlfile;
crosscheck backup;
delete noprompt expired backup;
delete noprompt obsolete;
release channel ch1;
release channel ch2;
}

3. 定时脚本

脚本

0级全备脚本rmanbk_0.sh

#!/bin/bash
#incremental level 1 database backup
export ORACLE_BASE=/u01/app/oracle
export ORACLE_HOME=$ORACLE_BASE/product/19.3/dbhome_1
#export ORACLE_HOME=$ORACLE_BASE/product/11.2.0/db_1
export ORACLE_SID=orcl
export PATH=$ORACLE_HOME/bin:$PATH
export LD_LIBRARY_PATH=$ORACLE_HOME/lib:/lib:/usr/lib

rman target / <<EOF
run {
allocate channel ch1 device type disk format '/tmp/test/full_0_%d_%s';
allocate channel ch2 device type disk format '/tmp/test/full_0_%d_%s';
sql'alter system switch logfile';
backup as compressed backupset incremental level 0 database plus archivelog delete input;
backup current controlfile;
crosscheck backup;
delete noprompt expired backup;
delete noprompt obsolete;
release channel ch1;
release channel ch2;
}
exit;
EOF

1级差异增量脚本rmanbk_1_diff.sh

#!/bin/bash
#incremental level 1 database backup
export ORACLE_BASE=/u01/app/oracle
export ORACLE_HOME=$ORACLE_BASE/product/19.3/dbhome_1
#export ORACLE_HOME=$ORACLE_BASE/product/11.2.0/db_1
export ORACLE_SID=orcl
export PATH=$ORACLE_HOME/bin:$PATH
export LD_LIBRARY_PATH=$ORACLE_HOME/lib:/lib:/usr/lib

rman target / <<EOF
run {
allocate channel ch1 device type disk format '/tmp/test/full_0_%d_%s';
allocate channel ch2 device type disk format '/tmp/test/full_0_%d_%s';
sql'alter system switch logfile';
backup as compressed backupset incremental level 1 database plus archivelog delete input;
backup current controlfile;
crosscheck backup;
delete noprompt expired backup;
delete noprompt obsolete;
release channel ch1;
release channel ch2;
}
exit;
EOF

1级累计增量脚本rmanbk_1_cumu.sh

#!/bin/bash
#incremental level 1 database backup
export ORACLE_BASE=/u01/app/oracle
export ORACLE_HOME=$ORACLE_BASE/product/19.3/dbhome_1
#export ORACLE_HOME=$ORACLE_BASE/product/11.2.0/db_1
export ORACLE_SID=orcl
export PATH=$ORACLE_HOME/bin:$PATH
export LD_LIBRARY_PATH=$ORACLE_HOME/lib:/lib:/usr/lib

rman target / <<EOF
run {
allocate channel ch1 device type disk format '/tmp/test/full_0_%d_%s';
allocate channel ch2 device type disk format '/tmp/test/full_0_%d_%s';
sql'alter system switch logfile';
backup as compressed backupset incremental level 1 cumulative database plus archivelog delete input;
backup current controlfile;
crosscheck backup;
delete noprompt expired backup;
delete noprompt obsolete;
release channel ch1;
release channel ch2;
}
exit;
EOF

计划任务

例如这样的备份策略：

周日全备，周一至周三差异，周四累积，周五周六差异

[oracle@db2 ~]$ crontab -l
30 22 * * 0 /bin/bash /home/oracle/rmanbk_0.sh >> /home/oracle/rmanbk_0.log 2>&1
30 22 * * 1,2,3,5,6 /bin/bash /home/oracle/rmanbk_1_diff.sh >> /home/oracle/rmanbk_1_diff.log 2>&1
30 22 * * 4 /bin/bash /home/oracle/rmanbk_1_cumu.sh >> /home/oracle/rmanbk_1_cumu.log 2>&1

备份脚本模板

方便复制修改

#零级备份脚本  
 run{
allocate channel c1 type disk;
allocate channel c2 type disk;
backup incremental level 0 database plus archivelog delete input ;
backup current controlfile; #rman控制文件自动备份没开就要加上
crosscheck backup;
report obsolete;#针对的是全备，并非0级，意义不大
delete noprompt obsolete;
delete noprompt expired backup;
}


#一级备份脚本  
run{
allocate channel c1 type disk;
allocate channel c2 type disk;
backup incremental level 1 database plus archivelog delete input ;
backup current controlfile;
tag='inc_1';
release channel c1;
release channel c2;
}

posted @ 2022-05-10 15:29 EverEternity 阅读(717) 评论(0) 编辑收藏举报

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