归档是将联机重做日志以文件的形式保存到硬盘，联机日志归档的前提条件是数据库要处于归档模式。当数据库处于 ARCHIVELOG 模式并进行日志切换时，后台进程 ARCH 会将联机重做日志的内容保存到归档日志中，当数据库出现介质故障时，使用数据文件备份、归档日志和联机重做日志可以完全恢复数据库到正常状态。
Oracle 数据库设置为归档模式之后，如果归档空间写满，数据库的 redo 文件不能归档，会出现数据库挂起的问题，导致 数据库无法使用。
一、查看数据库是否为归档模式
-- 节点1：归档模式
SQL> archive log list;
Database log mode Archive Mode
Automatic archival Enabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 14
Next log sequence to archive 17
Current log sequence 17
SQL> select log_mode from v$database;
LOG_MODE
------------
ARCHIVELOG
-- 节点2：非归档模式
SQL> archive log list;
Database log mode No Archive Mode
Automatic archival Disabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 11
Current log sequence 14
SQL> select log_mode from v$database;
LOG_MODE
------------
NOARCHIVELOG
二、打开或关闭归档模式
如果需要打开或关闭归档模式，在数据库处于 mount 状态时使用如下命令：
-- 打开归档模式
alter database archivelog;
-- 关闭归档模式
alter database noarchivelog;
把节点2 的数据库设置为归档模式，在节点2 执行如下操作：
1、正常停库，然后启动数据库到 mount 状态
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.
Total System Global Area 835104768 bytes
Fixed Size 2257840 bytes
Variable Size 583011408 bytes
Database Buffers 247463936 bytes
Redo Buffers 2371584 bytes
Database mounted.
2、使用 alter database 命令打开归档模式
SQL> alter database archivelog;
alter database archivelog
*
ERROR at line 1:
ORA-01126: database must be mounted in this instance and not open in any
instance
-- 命令出现错误的原因：在 rac 集群环境下，要设置一个节点为归档模式或非归档模式，必须关闭其他节点。
-- 关闭节点1
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
-- 在节点2 重新执行如下命令：
SQL> alter database archivelog;
Database altered.
3、打开数据库，查看归档状态
SQL> alter database open;
Database altered.
SQL> archive log list;
Database log mode Archive Mode
Automatic archival Enabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 13
Next log sequence to archive 16
Current log sequence 16
-- 数据库已经处于归档状态
三、配置归档的位置
当数据库处于归档模式时，进行日志切换时后台进程将自动生成归档日志。
1、查看归档进程数
初始化参数 LOG_ARCHIVE_MAX_PROCESSES 用于指定最大归档进程个数。通过改变该初始化参数的取值，可以动态地增加或减少归档进程的个数。
-- 查看归档进程数
SQL> show parameter LOG_ARCHIVE_MAX_PROCESSES
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
log_archive_max_processes integer 4
2、配置归档的位置
可以使用 LOG_ARCHIVE_DEST_n 配置多个归档位置：该参数最多可以指定 10 个归档位置。格式如下：
ALTER SYSTEM SET log_archive_dest_1 = 'location = 路径1';
ALTER SYSTEM SET log_archive_dest_2 = 'location = 路径2';
.....
（1）查看归档文件
可知当前归档位置为：+BAK/orcl/archivelog
SQL> select sequence#, name from v$archived_log;
SEQUENCE# NAME
---------- --------------------------------------------------------------------------
16 +BAK/orcl/archivelog/2021_08_08/thread_2_seq_16.319.1080028877
21 +BAK/orcl/archivelog/2021_08_08/thread_1_seq_21.320.1080050731
22 +BAK/orcl/archivelog/2021_08_08/thread_1_seq_22.318.1080060961
（2）修改归档日志的位置为：/home/oracle/archivelog
修改log_archive_dest_1 参数指向定义的归档位置：
SQL> alter system set log_archive_dest_1 = 'location=/home/oracle/archivelog' scope = both sid='*';
System altered.
SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /home/oracle/archivelog
Oldest online log sequence 23
Next log sequence to archive 26
Current log sequence 26
（3）手工切换日志：
SQL> alter system switch logfile;
System altered.
SQL> alter system switch logfile;
System altered.
（4）重新查看归档日志：
SQL> select sequence#, name from v$archived_log;
SEQUENCE# NAME
---------- --------------------------------------------------------------------------------
16 +BAK/orcl/archivelog/2021_08_08/thread_2_seq_16.319.1080028877
21 +BAK/orcl/archivelog/2021_08_08/thread_1_seq_21.320.1080050731
22 +BAK/orcl/archivelog/2021_08_08/thread_1_seq_22.318.1080060961
23 /home/oracle/archivelog/1_23_1079891135.dbf
24 /home/oracle/archivelog/1_24_1079891135.dbf
17 /home/oracle/archivelog/2_17_1079891135.dbf
18 /home/oracle/archivelog/2_18_1079891135.dbf
19 /home/oracle/archivelog/2_19_1079891135.dbf
25 /home/oracle/archivelog/1_25_1079891135.dbf
9 rows selected.
四、配置归档日志文件的名称格式
初始化参数 LOG_ARCHIVE_FORMAT 用于指定归档日志文件的名称格式。设置该初始化参数时，可以指定以下匹配符：
（1）%s：日志序列号；
（2）%S：日志序列号（带有前导 0）；
（3）%t：线程编号；
（4）%T：线程编号（带有前导 0）；
（5）%a：活动 ID 号；
（6）%d：数据库 ID 号；
（7）%r：RESETLOGS的ID值。
归档日志的文件名称格式设置如下：
SQL> alter system set LOG_ARCHIVE_FORMAT = 'thread_%T_seq_%S.%a.%r.%d' scope = spfile sid='*';
System altered.
-- 重启数据库使设置生效
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.
Total System Global Area 835104768 bytes
Fixed Size 2257840 bytes
Variable Size 570428496 bytes
Database Buffers 260046848 bytes
Redo Buffers 2371584 bytes
Database mounted.
Database opened.
查看参数 LOG_ARCHIVE_FORMAT 的值：
SQL> show parameter LOG_ARCHIVE_FORMAT
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
log_archive_format string thread_%T_seq_%S.%a.%r.%d
查看归档日志：
SQL> select sequence#, name from v$archived_log;
SEQUENCE# NAME
---------- ------------------------------------------------------------------------------------
16 +BAK/orcl/archivelog/2021_08_08/thread_2_seq_16.319.1080028877
21 +BAK/orcl/archivelog/2021_08_08/thread_1_seq_21.320.1080050731
22 +BAK/orcl/archivelog/2021_08_08/thread_1_seq_22.318.1080060961
23 /home/oracle/archivelog/1_23_1079891135.dbf
24 /home/oracle/archivelog/1_24_1079891135.dbf
17 /home/oracle/archivelog/2_17_1079891135.dbf
18 /home/oracle/archivelog/2_18_1079891135.dbf
19 /home/oracle/archivelog/2_19_1079891135.dbf
25 /home/oracle/archivelog/1_25_1079891135.dbf
20 /home/oracle/archivelog/2_20_1079891135.dbf
26 /home/oracle/archivelog/thread_0001_seq_0000000026.5fd299b3.1079891135.5f4366b6
27 /home/oracle/archivelog/thread_0001_seq_0000000027.5fd299b3.1079891135.5f4366b6
21 /home/oracle/archivelog/thread_0002_seq_0000000021.5fd299b3.1079891135.5f4366b6
22 /home/oracle/archivelog/thread_0002_seq_0000000022.5fd299b3.1079891135.5f4366b6
14 rows selected.
五、删除归档日志
1、手工删除归档日志文件
# 节点1
[oracle@rac1 ~]$ cd /home/oracle/archivelog/
[oracle@rac1 archivelog]$ ll
total 3576
-rw-r----- 1 oracle asmadmin 3208704 Aug 8 18:17 1_23_1079891135.dbf
-rw-r----- 1 oracle asmadmin 1024 Aug 8 18:17 1_24_1079891135.dbf
-rw-r----- 1 oracle asmadmin 1024 Aug 8 18:18 1_25_1079891135.dbf
-rw-r----- 1 oracle asmadmin 437248 Aug 8 19:47 thread_0001_seq_0000000026.5fd299b3.1079891135.5f4366b6
-rw-r----- 1 oracle asmadmin 1024 Aug 8 19:47 thread_0001_seq_0000000027.5fd299b3.1079891135.5f4366b6
[oracle@rac1 archivelog]$ rm 1*
[oracle@rac1 archivelog]$ ll
total 432
-rw-r----- 1 oracle asmadmin 437248 Aug 8 19:47 thread_0001_seq_0000000026.5fd299b3.1079891135.5f4366b6
-rw-r----- 1 oracle asmadmin 1024 Aug 8 19:47 thread_0001_seq_0000000027.5fd299b3.1079891135.5f4366b6
# 节点2
[oracle@rac2 ~]$ cd /home/oracle/archivelog/
[oracle@rac2 archivelog]$ ll
total 33892
-rw-r----- 1 oracle asmadmin 34569216 Aug 8 18:17 2_17_1079891135.dbf
-rw-r----- 1 oracle asmadmin 1024 Aug 8 18:17 2_18_1079891135.dbf
-rw-r----- 1 oracle asmadmin 1024 Aug 8 18:18 2_19_1079891135.dbf
-rw-r----- 1 oracle asmadmin 70144 Aug 8 18:48 2_20_1079891135.dbf
-rw-r----- 1 oracle asmadmin 46080 Aug 8 19:47 thread_0002_seq_0000000021.5fd299b3.1079891135.5f4366b6
-rw-r----- 1 oracle asmadmin 1024 Aug 8 19:47 thread_0002_seq_0000000022.5fd299b3.1079891135.5f4366b6
[oracle@rac2 archivelog]$ rm 2*
[oracle@rac2 archivelog]$ ll
total 52
-rw-r----- 1 oracle asmadmin 46080 Aug 8 19:47 thread_0002_seq_0000000021.5fd299b3.1079891135.5f4366b6
-rw-r----- 1 oracle asmadmin 1024 Aug 8 19:47 thread_0002_seq_0000000022.5fd299b3.1079891135.5f4366b6
查看归档日志：
SQL> select sequence#, name from v$archived_log;
SEQUENCE# NAME
-----------------------------------------------------------------------------------------------
16 +BAK/orcl/archivelog/2021_08_08/thread_2_seq_16.319.1080028877
21 +BAK/orcl/archivelog/2021_08_08/thread_1_seq_21.320.1080050731
22 +BAK/orcl/archivelog/2021_08_08/thread_1_seq_22.318.1080060961
23 /home/oracle/archivelog/1_23_1079891135.dbf
24 /home/oracle/archivelog/1_24_1079891135.dbf
17 /home/oracle/archivelog/2_17_1079891135.dbf
18 /home/oracle/archivelog/2_18_1079891135.dbf
19 /home/oracle/archivelog/2_19_1079891135.dbf
25 /home/oracle/archivelog/1_25_1079891135.dbf
20 /home/oracle/archivelog/2_20_1079891135.dbf
26 /home/oracle/archivelog/thread_0001_seq_0000000026.5fd299b3.1079891135.5f4366b6
27 /home/oracle/archivelog/thread_0001_seq_0000000027.5fd299b3.1079891135.5f4366b6
21 /home/oracle/archivelog/thread_0002_seq_0000000021.5fd299b3.1079891135.5f4366b6
22 /home/oracle/archivelog/thread_0002_seq_0000000022.5fd299b3.1079891135.5f4366b6
14 rows selected.
虽然物理文件已经删除，但是归档日志文件的信息还在。
2、用 RMAN 删除数据库记录的归档列表信息
（1）进入 rman，查看归档日志文件的状态：
RMAN> list archivelog all;
using target database control file instead of recovery catalog
List of Archived Log Copies for database with db_unique_name ORCL
=====================================================================
Key Thrd Seq S Low Time
------- ---- ------- - ---------
2 1 21 A 07-AUG-21
Name: +BAK/orcl/archivelog/2021_08_08/thread_1_seq_21.320.1080050731
3 1 22 A 08-AUG-21
Name: +BAK/orcl/archivelog/2021_08_08/thread_1_seq_22.318.1080060961
4 1 23 A 08-AUG-21
Name: /home/oracle/archivelog/1_23_1079891135.dbf
5 1 24 A 08-AUG-21
Name: /home/oracle/archivelog/1_24_1079891135.dbf
9 1 25 A 08-AUG-21
Name: /home/oracle/archivelog/1_25_1079891135.dbf
11 1 26 A 08-AUG-21
Name: /home/oracle/archivelog/thread_0001_seq_0000000026.5fd299b3.1079891135.5f4366b6
12 1 27 A 08-AUG-21
Name: /home/oracle/archivelog/thread_0001_seq_0000000027.5fd299b3.1079891135.5f4366b6
1 2 16 A 07-AUG-21
Name: +BAK/orcl/archivelog/2021_08_08/thread_2_seq_16.319.1080028877
6 2 17 A 08-AUG-21
Name: /home/oracle/archivelog/2_17_1079891135.dbf
7 2 18 A 08-AUG-21
Name: /home/oracle/archivelog/2_18_1079891135.dbf
8 2 19 A 08-AUG-21
Name: /home/oracle/archivelog/2_19_1079891135.dbf
10 2 20 A 08-AUG-21
Name: /home/oracle/archivelog/2_20_1079891135.dbf
13 2 21 A 08-AUG-21
Name: /home/oracle/archivelog/thread_0002_seq_0000000021.5fd299b3.1079891135.5f4366b6
14 2 22 A 08-AUG-21
Name: /home/oracle/archivelog/thread_0002_seq_0000000022.5fd299b3.1079891135.5f4366b6
（2）更新归档日志信息
RMAN> crosscheck archivelog all;
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=61 instance=orcl2 device type=DISK
validation succeeded for archived log
archived log file name=+BAK/orcl/archivelog/2021_08_08/thread_1_seq_21.320.1080050731 RECID=2 STAMP=1080065388
validation succeeded for archived log
archived log file name=+BAK/orcl/archivelog/2021_08_08/thread_1_seq_22.318.1080060961 RECID=3 STAMP=1080065388
validation failed for archived log
archived log file name=/home/oracle/archivelog/1_23_1079891135.dbf RECID=4 STAMP=1080065865
validation failed for archived log
archived log file name=/home/oracle/archivelog/1_24_1079891135.dbf RECID=5 STAMP=1080065866
validation failed for archived log
archived log file name=/home/oracle/archivelog/1_25_1079891135.dbf RECID=9 STAMP=1080065896
validation failed for archived log
archived log file name=/home/oracle/archivelog/thread_0001_seq_0000000026.5fd299b3.1079891135.5f4366b6 RECID=11 STAMP=1080071232
validation failed for archived log
archived log file name=/home/oracle/archivelog/thread_0001_seq_0000000027.5fd299b3.1079891135.5f4366b6 RECID=12 STAMP=1080071232
validation succeeded for archived log
archived log file name=+BAK/orcl/archivelog/2021_08_08/thread_2_seq_16.319.1080028877 RECID=1 STAMP=1080065388
validation failed for archived log
archived log file name=/home/oracle/archivelog/2_17_1079891135.dbf RECID=6 STAMP=1080065872
validation failed for archived log
archived log file name=/home/oracle/archivelog/2_18_1079891135.dbf RECID=7 STAMP=1080065880
validation failed for archived log
archived log file name=/home/oracle/archivelog/2_19_1079891135.dbf RECID=8 STAMP=1080065881
validation failed for archived log
archived log file name=/home/oracle/archivelog/2_20_1079891135.dbf RECID=10 STAMP=1080067716
validation succeeded for archived log
archived log file name=/home/oracle/archivelog/thread_0002_seq_0000000021.5fd299b3.1079891135.5f4366b6 RECID=13 STAMP=1080071241
validation succeeded for archived log
archived log file name=/home/oracle/archivelog/thread_0002_seq_0000000022.5fd299b3.1079891135.5f4366b6 RECID=14 STAMP=1080071248
Crosschecked 14 objects
（3）删除失效的归档文件信息
RMAN> delete expired archivelog all;
released channel: ORA_DISK_1
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=61 instance=orcl2 device type=DISK
List of Archived Log Copies for database with db_unique_name ORCL
=====================================================================
Key Thrd Seq S Low Time
------- ---- ------- - ---------
4 1 23 X 08-AUG-21
Name: /home/oracle/archivelog/1_23_1079891135.dbf
.......
Do you really want to delete the above objects (enter YES or NO)? yes
deleted archived log
archived log file name=/home/oracle/archivelog/1_23_1079891135.dbf RECID=4 STAMP=1080065865
deleted archived log
archived log file name=/home/oracle/archivelog/1_24_1079891135.dbf RECID=5 STAMP=1080065866
deleted archived log
archived log file name=/home/oracle/archivelog/1_25_1079891135.dbf RECID=9 STAMP=1080065896
deleted archived log
archived log file name=/home/oracle/archivelog/thread_0001_seq_0000000026.5fd299b3.1079891135.5f4366b6 RECID=11 STAMP=1080071232
deleted archived log
archived log file name=/home/oracle/archivelog/thread_0001_seq_0000000027.5fd299b3.1079891135.5f4366b6 RECID=12 STAMP=1080071232
deleted archived log
archived log file name=/home/oracle/archivelog/2_17_1079891135.dbf RECID=6 STAMP=1080065872
deleted archived log
archived log file name=/home/oracle/archivelog/2_18_1079891135.dbf RECID=7 STAMP=1080065880
deleted archived log
archived log file name=/home/oracle/archivelog/2_19_1079891135.dbf RECID=8 STAMP=1080065881
deleted archived log
archived log file name=/home/oracle/archivelog/2_20_1079891135.dbf RECID=10 STAMP=1080067716
Deleted 9 EXPIRED objects
（4）重新查看归档日志
使用RMAN 命令删除归档后，v$archived_log 视图中的 name 列为空，但其他列的信息仍然存在。
SQL> select sequence#, name from v$archived_log;
SEQUENCE# NAME
----------------------------------------------------------------------------------------------
16 +BAK/orcl/archivelog/2021_08_08/thread_2_seq_16.319.1080028877
21 +BAK/orcl/archivelog/2021_08_08/thread_1_seq_21.320.1080050731
22 +BAK/orcl/archivelog/2021_08_08/thread_1_seq_22.318.1080060961
23
24
17
18
19
25
20
26
27
21 /home/oracle/archivelog/thread_0002_seq_0000000021.5fd299b3.1079891135.5f4366b6
22 /home/oracle/archivelog/thread_0002_seq_0000000022.5fd299b3.1079891135.5f4366b6
14 rows selected.
3、清除 v$archived_log 视图中的过期信息
使用RMAN 命令删除归档后，v$archived_log 视图中的 name 列为空，但其他列的信息仍然存在。出现这种现象的原因是因为使用 RMAN 命令在删除归档日志的时候不能够清除控制文件中的内容。
（1）清除控制文件中关于 v$archived_log 的信息
SQL> execute sys.dbms_backup_restore.resetCfileSection(11);
PL/SQL procedure successfully completed.
-- 查询发现 v$archived_log 视图中的信息全部被清除了
SQL> select sequence#, name from v$archived_log;
no rows selected
（2）将未过期的归档文件信息重新注册到控制文件中（两个节点同时进行）
RMAN> catalog start with '/home/oracle/archivelog/';
searching for all files that match the pattern /home/oracle/archivelog/
List of Files Unknown to the Database
=====================================
File Name: /home/oracle/archivelog/thread_0002_seq_0000000022.5fd299b3.1079891135.5f4366b6
File Name: /home/oracle/archivelog/thread_0002_seq_0000000021.5fd299b3.1079891135.5f4366b6
Do you really want to catalog the above files (enter YES or NO)? yes
cataloging files...
cataloging done
List of Cataloged Files
=======================
File Name: /home/oracle/archivelog/thread_0002_seq_0000000022.5fd299b3.1079891135.5f4366b6
File Name: /home/oracle/archivelog/thread_0002_seq_0000000021.5fd299b3.1079891135.5f4366b6
重新查看归档日志：
SQL> select sequence#, name from v$archived_log;
SEQUENCE# NAME
----------------------------------------------------------------------------------------
22 /home/oracle/archivelog/thread_0002_seq_0000000022.5fd299b3.1079891135.5f4366b6
21 /home/oracle/archivelog/thread_0002_seq_0000000021.5fd299b3.1079891135.5f4366b6