聊聊RMAN的ARCHIVELOG DELETION参数

RMAN是Oracle推出的官方备份还原工具。经过几个大版本的发展，RMAN已经支持多种备份介质和恢复策略的主要工具，也是业界普遍认可

RMAN是Oracle推出的官方备份还原工具。经过几个大版本的发展，RMAN已经支持多种备份介质和恢复策略的主要工具，也是业界普遍认可是Oracle备份还原官方策略。

Archivelog是Oracle备份还原策略的重要组成元素，不完全备份+连续的归档日志可以让我们将数据库恢复到发生故障点，实现数据的无损失恢复。但是，现实生活中archive log给没有经验的运维人员也带来了不少的问题，归档空间占满引起Hang住、瞬间归档日志过多生成引起问题等。一些前辈也在不断强调“归档模式不美好”。

在RMAN工作参数中，针对archive log，是可以设置专门的删除策略（Deletion）。在实践领域中，已经备份过或者确保安全传输的归档日志，其实就可以删除了，特别是在有限的Fast Recovery Area管理模式下。对于自动删除archive log的策略，比较常见的是applied to standby和shipped to standby，也就是Data Guard场景下。

本篇介绍简单的backed up参数使用情况，并通过一系列实验去研究该参数影响下Oracle和RMAN的工作行为特性。

1、基本参数和实验环境

笔者使用Oracle 11gR2进行测试，具体版本编号为11.2.0.4。

SQL> select * from v$version;

BANNER

--------------------------------------------------------------------------------

Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production

PL/SQL Release 11.2.0.3.0 - Production

CORE    11.2.0.3.0    Production

TNS for Linux: Version 11.2.0.3.0 - Production

NLSRTL Version 11.2.0.3.0 – Production

默认情况下，archivelog deletion policy参数为NONE。

RMAN> show all;     

RMAN configuration parameters for database with db_unique_name XXXXDB are:

CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default

（篇幅原因，有省略……）

CONFIGURE ARCHIVELOG DELETION POLICY TO NONE; # default

该参数常见的集中取值如下：

configure archivelog deletion policy to backed up 2 times to sbt;

configure archivelog deletion policy to backed up 1 times to device type disk;

configure archivelog deletion policy to applied on standby;  --DG专用

configure archivelog deletion policy to shipped on standby;  --DG专用

configure archivelog deletion policy clear;

研究archivelog行为最好的工具视图是v$archived_log。很多DBA喜欢从操作系统层面删除归档日志，但是这种方式是不会直接被Oracle控制文件认可，所以建议使用RMAN或者官方工具来做。

--已归档未删除日志

SQL> select count(*) from v$archived_log where archived='YES' and deleted='NO';

COUNT(*)

----------

13

2、第一轮备份测试实验

首先我们修改archivelog deletion policy参数，设置为“两次备份后即可以删除”。

RMAN> configure archivelog deletion policy to backed up 2 times to device type disk;

new RMAN configuration parameters:

CONFIGURE ARCHIVELOG DELETION POLICY TO BACKED UP 2 TIMES TO DISK;

new RMAN configuration parameters are successfully stored

手工备份数据库和归档日志，不进行删除动作。

RMAN> backup database plus archivelog;

Starting backup at 21-SEP-15

current log archived

allocated channel: ORA_DISK_1

channel ORA_DISK_1: SID=16 device type=DISK

channel ORA_DISK_1: starting archived log backup set

channel ORA_DISK_1: specifying archived log(s) in backup set

input archived log thread=1 sequence=100 RECID=12 STAMP=890690423

input archived log thread=1 sequence=101 RECID=13 STAMP=890712061

input archived log thread=1 sequence=102 RECID=14 STAMP=890727732

input archived log thread=1 sequence=103 RECID=15 STAMP=890776815

input archived log thread=1 sequence=104 RECID=16 STAMP=890776833

input archived log thread=1 sequence=105 RECID=17 STAMP=890805616

input archived log thread=1 sequence=106 RECID=18 STAMP=890814181

input archived log thread=1 sequence=107 RECID=19 STAMP=890820201

input archived log thread=1 sequence=108 RECID=20 STAMP=890859629

input archived log thread=1 sequence=109 RECID=21 STAMP=890892046

input archived log thread=1 sequence=110 RECID=22 STAMP=890900632

input archived log thread=1 sequence=111 RECID=23 STAMP=890906655

input archived log thread=1 sequence=112 RECID=24 STAMP=890942416

input archived log thread=1 sequence=113 RECID=25 STAMP=890990204

channel ORA_DISK_1: starting piece 1 at 21-SEP-15

channel ORA_DISK_1: finished piece 1 at 21-SEP-15

piece handle=/u01/app/oracle/fast_recovery_area/XXXXDB/backupset/2015_09_21/o1_mf_annnn_TAG20150921T091644_bzypmwty_.bkp tag=TAG20150921T091644 

（篇幅原因，省略部分……）

Finished Control File and SPFILE Autobackup at 21-SEP-15

此时，归档日志被备份，并且没有删除。

--多出来的两个是由于进行备份时候自动会有switch log

SQL> select count(*) from v$archived_log where archived='YES' and deleted='NO';

COUNT(*)

----------

15

下面进行第二次实验。

RMAN> backup database plus archivelog;

Starting backup at 21-SEP-15

current log archived

using channel ORA_DISK_1

channel ORA_DISK_1: starting archived log backup set

channel ORA_DISK_1: specifying archived log(s) in backup set

input archived log thread=1 sequence=100 RECID=12 STAMP=890690423

input archived log thread=1 sequence=101 RECID=13 STAMP=890712061

input archived log thread=1 sequence=102 RECID=14 STAMP=890727732

input archived log thread=1 sequence=103 RECID=15 STAMP=890776815

input archived log thread=1 sequence=104 RECID=16 STAMP=890776833

input archived log thread=1 sequence=105 RECID=17 STAMP=890805616

input archived log thread=1 sequence=106 RECID=18 STAMP=890814181

input archived log thread=1 sequence=107 RECID=19 STAMP=890820201

input archived log thread=1 sequence=108 RECID=20 STAMP=890859629

input archived log thread=1 sequence=109 RECID=21 STAMP=890892046

input archived log thread=1 sequence=110 RECID=22 STAMP=890900632

input archived log thread=1 sequence=111 RECID=23 STAMP=890906655

input archived log thread=1 sequence=112 RECID=24 STAMP=890942416

input archived log thread=1 sequence=113 RECID=25 STAMP=890990204

input archived log thread=1 sequence=114 RECID=26 STAMP=890990263

input archived log thread=1 sequence=115 RECID=27 STAMP=890990391

channel ORA_DISK_1: starting piece 1 at 21-SEP-15

channel ORA_DISK_1: finished piece 1 at 21-SEP-15

piece handle=/u01/app/oracle/fast_recovery_area/XXXXDB/backupset/2015_09_21/o1_mf_annnn_TAG20150921T091951_bzypsqj3_.bkp tag=TAG20150921T091951 

（篇幅原因，有省略……）

Finished Control File and SPFILE Autobackup at 21-SEP-15

第二次备份，之前备份过的日志还出现在自动备份的列表中。但是，在第二次备份的时候，已经备份过两次（deletion policy）的日志并没有自动删除。

SQL> select count(*) from v$archived_log where archived='YES' and deleted='NO';

COUNT(*)

----------

17

归档日志还在fast recovery area中。

[oracle@Databaseintrawebpro fast_recovery_area]$ du -h

19M    ./XXXXDB/autobackup/2015_09_21

9.4M    ./XXXXDB/autobackup/2015_09_17

29M    ./XXXXDB/autobackup

151M    ./XXXXDB/onlinelog

6.0G    ./XXXXDB/backupset/2015_09_21

108K    ./XXXXDB/backupset/2015_09_17

6.0G    ./XXXXDB/backupset

125M    ./XXXXDB/archivelog/2015_09_19

27M    ./XXXXDB/archivelog/2015_09_21

4.0K    ./XXXXDB/archivelog/2015_09_15

127M    ./XXXXDB/archivelog/2015_09_18

121M    ./XXXXDB/archivelog/2015_09_20

4.0K    ./XXXXDB/archivelog/2015_09_16

32M    ./XXXXDB/archivelog/2015_09_17

431M    ./XXXXDB/archivelog

9.4M    ./XXXXDB/controlfile

6.6G    ./XXXXDB

6.6G    .

此时，归档日志和备份次数，在v$archived_log中可以方便的找出来。

SQL> alter system switch logfile;

System altered

SQL> select count(*) from v$archived_log where archived='YES' and deleted='NO';

COUNT(*)

----------

18

--注意这些已经备份过两次的recid编号

SQL> select recid, sequence#, archived, deleted, backup_count from v$archived_log where backup_count>1;

RECID  SEQUENCE# ARCHIVED DELETED BACKUP_COUNT

---------- ---------- -------- ------- ------------

12        100 YES      NO                2

13        101 YES      NO                2

14        102 YES      NO                2

15        103 YES      NO                2

16        104 YES      NO                2

17        105 YES      NO                2

18        106 YES      NO                2

19        107 YES      NO                2

20        108 YES      NO                2

21        109 YES      NO                2

22        110 YES      NO                2

23        111 YES      NO                2

24        112 YES      NO                2

25        113 YES      NO                2

26        114 YES      NO                2

15 rows selected

进行第三次备份。

RMAN> backup database plus archivelog;

Starting backup at 21-SEP-15

current log archived

allocated channel: ORA_DISK_1

channel ORA_DISK_1: SID=498 device type=DISK

skipping archived logs of thread 1 from sequence 100 to 114; already backed up

channel ORA_DISK_1: starting archived log backup set

channel ORA_DISK_1: specifying archived log(s) in backup set

input archived log thread=1 sequence=115 RECID=27 STAMP=890990391

input archived log thread=1 sequence=116 RECID=28 STAMP=890990481

input archived log thread=1 sequence=117 RECID=29 STAMP=890990667

input archived log thread=1 sequence=118 RECID=30 STAMP=890993128

channel ORA_DISK_1: starting piece 1 at 21-SEP-15

channel ORA_DISK_1: finished piece 1 at 21-SEP-15

piece 

（篇幅原因，有省略…….）

Finished Control File and SPFILE Autobackup at 21-SEP-15

注意：备份过两次的日志，没有出现在RMAN自动备份的列表中。这里我们定义到了删除策略的一个行为：当满足删除条件的时候，归档日志是不会进入备份集合列表的。

归档日志信息：

SQL> select recid, sequence#, archived, deleted, backup_count from v$archived_log where backup_count>1;

RECID  SEQUENCE# ARCHIVED DELETED BACKUP_COUNT

---------- ---------- -------- ------- ------------

12        100 YES      YES                2

13        101 YES      YES                2

14        102 YES      YES                2

15        103 YES      YES                2

16        104 YES      YES                2

17        105 YES      YES                2

18        106 YES      YES                2

19        107 YES      YES                2

20        108 YES      YES                2

21        109 YES      YES                2

22        110 YES      YES                2

23        111 YES      YES                2

24        112 YES      YES                2

25        113 YES      YES                2

26        114 YES      NO                2

27        115 YES      NO                2

28        116 YES      NO                2

17 rows selected

注意：一部分归档日志被删除，但是并没有所有上次备份过两次的日志都删除掉了，比如recid=26的日志。此时，备份fast recovery area空间情况发生了变化。

[oracle@Databaseintrawebpro fast_recovery_area]$ du -h

29M    ./XXXXDB/autobackup/2015_09_21

4.0K    ./XXXXDB/autobackup/2015_09_17

29M    ./XXXXDB/autobackup

151M    ./XXXXDB/onlinelog

5.5G    ./XXXXDB/backupset/2015_09_21

4.0K    ./XXXXDB/backupset/2015_09_17

5.5G    ./XXXXDB/backupset

4.0K    ./XXXXDB/archivelog/2015_09_19

2.5M    ./XXXXDB/archivelog/2015_09_21

4.0K    ./XXXXDB/archivelog/2015_09_15

4.0K    ./XXXXDB/archivelog/2015_09_18

4.0K    ./XXXXDB/archivelog/2015_09_20

4.0K    ./XXXXDB/archivelog/2015_09_16

4.0K    ./XXXXDB/archivelog/2015_09_17

2.6M    ./XXXXDB/archivelog

9.4M    ./XXXXDB/controlfile

5.7G    ./XXXXDB

5.7G    .

在alert log中，我们看到了Oracle自动删除的动作。

Mon Sep 21 09:24:27 2015

Expanded controlfile section 11 from 28 to 56 records

Requested to grow by 28 records; added 1 blocks of records

Archived Log entry 29 added for thread 1 sequence 117 ID 0x774e158c dest 1:

Mon Sep 21 10:05:28 2015

ALTER SYSTEM ARCHIVE LOG

Mon Sep 21 10:05:28 2015

Thread 1 advanced to log sequence 119 (LGWR switch)

Current log# 2 seq# 119 mem# 0: /u01/app/oracle/oradata/XXXXDB/onlinelog/o1_mf_2_bxzzjj5w_.log

Current log# 2 seq# 119 mem# 1: /u01/app/oracle/fast_recovery_area/XXXXDB/onlinelog/o1_mf_2_bxzzjj80_.log

Archived Log entry 30 added for thread 1 sequence 118 ID 0x774e158c dest 1:

Mon Sep 21 10:05:47 2015

Deleted Oracle managed file /u01/app/oracle/fast_recovery_area/XXXXDB/backupset/2015_09_17/o1_mf_annnn_TAG20150917T195557_bzoblfck_.bkp

Deleted Oracle managed file /u01/app/oracle/fast_recovery_area/XXXXDB/archivelog/2015_09_17/o1_mf_1_100_bzokvqj0_.arc

Deleted Oracle managed file /u01/app/oracle/fast_recovery_area/XXXXDB/autobackup/2015_09_17/o1_mf_s_890682958_bzoblglw_.bkp

Deleted Oracle managed file /u01/app/oracle/fast_recovery_area/XXXXDB/archivelog/2015_09_18/o1_mf_1_101_bzp6zx31_.arc

Deleted Oracle managed file /u01/app/oracle/fast_recovery_area/XXXXDB/archivelog/2015_09_18/o1_mf_1_102_bzpp9nln_.arc

Deleted Oracle managed file /u01/app/oracle/fast_recovery_area/XXXXDB/archivelog/2015_09_18/o1_mf_1_103_bzr67h1h_.arc

Deleted Oracle managed file /u01/app/oracle/fast_recovery_area/XXXXDB/archivelog/2015_09_18/o1_mf_1_104_bzr6812s_.arc

Deleted Oracle managed file /u01/app/oracle/fast_recovery_area/XXXXDB/archivelog/2015_09_19/o1_mf_1_105_bzs2cj5y_.arc

Deleted Oracle managed file /u01/app/oracle/fast_recovery_area/XXXXDB/archivelog/2015_09_19/o1_mf_1_106_bzsbq54p_.arc

Deleted Oracle managed file /u01/app/oracle/fast_recovery_area/XXXXDB/archivelog/2015_09_19/o1_mf_1_107_bzsjm99v_.arc

Deleted Oracle managed file /u01/app/oracle/fast_recovery_area/XXXXDB/archivelog/2015_09_19/o1_mf_1_108_bztq3f2v_.arc

Deleted Oracle managed file /u01/app/oracle/fast_recovery_area/XXXXDB/archivelog/2015_09_20/o1_mf_1_109_bzvprgf1_.arc

Deleted Oracle managed file /u01/app/oracle/fast_recovery_area/XXXXDB/archivelog/2015_09_20/o1_mf_1_110_bzvz4rj7_.arc

Deleted Oracle managed file /u01/app/oracle/fast_recovery_area/XXXXDB/archivelog/2015_09_20/o1_mf_1_111_bzw50zmb_.arc

Deleted Oracle managed file /u01/app/oracle/fast_recovery_area/XXXXDB/archivelog/2015_09_20/o1_mf_1_112_bzx7yj9g_.arc

Deleted Oracle managed file /u01/app/oracle/fast_recovery_area/XXXXDB/archivelog/2015_09_21/o1_mf_1_113_bzypmw8c_.arc

Deleted Oracle managed file /u01/app/oracle/fast_recovery_area/XXXXDB/backupset/2015_09_21/o1_mf_annnn_TAG20150921T091644_bzypmwty_.bkp

Mon Sep 21 10:05:58 2015

Deleted Oracle managed file /u01/app/oracle/fast_recovery_area/XXXXDB/backupset/2015_09_21/o1_mf_nnndf_TAG20150921T091647_bzypn055_.bkp

Mon Sep 21 10:06:15 2015

ALTER SYSTEM ARCHIVE LOG

Mon Sep 21 10:06:15 2015

Thread 1 advanced to log sequence 120 (LGWR switch)

Current log# 3 seq# 120 mem# 0: /u01/app/oracle/oradata/XXXXDB/onlinelog/o1_mf_3_bxzzjl0z_.log

Current log# 3 seq# 120 mem# 1: /u01/app/oracle/fast_recovery_area/XXXXDB/onlinelog/o1_mf_3_bxzzjl35_.log

Archived Log entry 31 added for thread 1 sequence 119 ID 0x774e158c dest 1: