本次先来介绍一下在rac环境下，开启归档的最简单的方法。
环境：oracle11g RAC 11.2.0.4

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登陆sqlplus
Last login: Wed Jul 29 09:25:43 2015 from 10.112.16.22
[root@hyldb1 ~]# su - oracle
[oracle@hyldb1 ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.4.0 Production on Wed Jul 29 09:29:44 2015

Copyright (c) 1982, 2013, Oracle. All rights reserved.

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, Real Application Clusters, Automatic Storage Management, OLAP,
Data Mining and Real Application Testing options

查看ASM空间使用率
SQL> select group_number,name,total_mb,free_mb from v$asm_diskgroup;

GROUP_NUMBER NAME TOTAL_MB FREE_MB
------------ ------------------------------ ---------- ----------
1 OCR_ARCH 2048000 2042322
2 OCR_DATA 26112000 23640108
3 OCR_VOTE 61440 60514

查看归档状态
SQL> archive log list;
Database log mode No Archive Mode
Automatic archival Disabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 29061
Current log sequence 29065

SQL> show user
USER is "SYS"

节点1、2，分别关库，或使用命令：srvctl stop instance -d hyl来关闭所有实例。
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.

节点1，启库到mount
SQL> startup mount;
ORACLE instance started.

Total System Global Area 3.9284E+10 bytes
Fixed Size 2261608 bytes
Variable Size 7516196248 bytes
Database Buffers 3.1675E+10 bytes
Redo Buffers 89997312 bytes
Database mounted.

查看节点1的状态
SQL> select status from gv$instance;

STATUS
------------
MOUNTED

为节点1开启归档
开启归档
SQL> alter database archivelog;
Database altered.

查看归档状态，可以看到默认归档路径为USE_DB_RECOVERY_FILE_DEST
SQL> archive log list;
Database log mode Archive Mode
Automatic archival Enabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 29061
Next log sequence to archive 29065
Current log sequence 29065

节点1启库
SQL> alter database open;

Database altered.

SQL> select status,instance_name from gv$instance;

STATUS INSTANCE_NAME
------------ ----------------
OPEN hyl1

SQL> archive log list;
Database log mode Archive Mode
Automatic archival Enabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 29061
Next log sequence to archive 29065
Current log sequence 29065

来看一下，归档路径的信息，默认是直接指向了ASM中的路径
SQL> show parameter recover

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_recovery_file_dest string +OCR_ARCH
db_recovery_file_dest_size big integer 4407M
db_unrecoverable_scn_tracking boolean TRUE
recovery_parallelism integer 0

节点2启库：
SQL> startup;
ORACLE instance started.

Total System Global Area 3.9284E+10 bytes
Fixed Size 2261608 bytes
Variable Size 6710889880 bytes
Database Buffers 3.2481E+10 bytes
Redo Buffers 89997312 bytes
Database mounted.
Database opened.

查看集群实例启动状态
SQL> select status,instance_name from gv$instance;

STATUS INSTANCE_NAME
------------ ----------------
OPEN hyl2
OPEN hyl1

查看节点2的归档状态
SQL> archive log list;
Database log mode Archive Mode
Automatic archival Enabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 48485
Next log sequence to archive 48489
Current log sequence 48489

查看db_recovery_file_dest信息
SQL> show parameter recover