直接登录相应的用户就可以了。
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步骤：直接在命令行输入sqlconn username/password；即可完成切换.
解释：每个用户都只能默认一个数据库，不可能出现多个数据库。所以直接切换到需要的用户下即可完成操作。
1、在不退出sqlplus的情况下，直接在命令行输入conn username/password；即可完成切换。
2、在退出sqlplus的情况下，windows下：set ORACLE_SID=db_name; linux下：export ORACLE_SID = db_name再登录相应的用户即可完成切换。
3、创建用户命令：create user usernamer identified by passwd；
4、给用户赋权限：grant connect,resource,dba to username;
直接登录相应的用户就可以了。
步骤：直接在命令行输入sqlconn
username/password；即可完成切换.
解释：每个用户都只能默认一个数据库，不可能出现多个数据库。所以直接切换到需要的用户下即可完成操作。
1、在数据库服务器的开始菜单中找到Datebase Configuration Assistant。
2、在创建画面第一步选择：创建新数据库，点击下一步。
3、根据需求选择自己的数据库类型(一般默认)后，跳转到全局数据库名这个画面时，重点来了：新建数据库名称不能和已经存在的任何一个数据库名称相同。
4、在管理帐户密码界面，可以与别的数据库管理帐户密码相同也可以不同，需注意的是，Oracle数据库默认是区分密码大小写的。
5、跳转到Oracle内存分配大小页面，这里建议将Oracle内存调整为物理主机内存的70%。
6、点击完成后，等待数据库创建完成。
7、数据库创建完成后，用sqlplus 语句连接数据库，在同一服务器上建立多个Oracle数据库操作完成。
oracle dg 三大模式切换
1、最大性能模式MAXIMUM PERFORMANCE --默认模式，最大性能模式特点。
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SQL select database_role,protection_mode,protection_level from v$database;
DATABASE_ROLE PROTECTION_MODE PROTECTION_LEVEL
---------------- -------------------- --------------------
PRIMARY MAXIMUM PERFORMANCE MAXIMUM PERFORMANCE
SQL col dest_name for a25
SQL select dest_name,status from v$archive_dest_status;
DEST_NAME STATUS
------------------------- ---------
LOG_ARCHIVE_DEST_1 VALID
LOG_ARCHIVE_DEST_2 VALID
SQL show parameter log_archive
NAME TYPE VALUE
------------------------------------ ----------- ---------------------------
log_archive_config string dg_config=(orcl,db01)
log_archive_dest_1 string location=/home/oracle/arch_orc
l valid_for=(all_logfiles,all_
roles) db_unique_name=orcl
log_archive_dest_2 string service=db_db01 LGWR ASYNC val
id_for=(online_logfiles,primar
y_roles) db_unique_name=db01
SQL archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /home/oracle/arch_orcl
Oldest online log sequence 31
Next log sequence to archive 33
Current log sequence 33
192.168.1.183
SQL select database_role,protection_mode,protection_level from v$database;
DATABASE_ROLE PROTECTION_MODE PROTECTION_LEVEL
---------------- -------------------- --------------------
PHYSICAL STANDBY MAXIMUM PERFORMANCE MAXIMUM PERFORMANCE
SQL col dest_name for a25
SQL select dest_name,status from v$archive_dest_status;
DEST_NAME STATUS
------------------------- ---------
LOG_ARCHIVE_DEST_1 VALID
LOG_ARCHIVE_DEST_2 VALID
SQL show parameter log_archive
NAME TYPE VALUE
------------------------------------ ----------- ---------------------------
log_archive_config string dg_config=(db01,orcl)
log_archive_dest_1 string location=/home/oracle/arch_db0
1 valid_for=(all_logfiles,all_
roles) db_unique_name=db01
log_archive_dest_2 string service=db_orcl LGWR ASYNC val
id_for=(online_logfiles,primar
y_roles) db_unique_name=orcl
SQL archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /home/oracle/arch_orcl
Oldest online log sequence 31
Next log sequence to archive 33
Current log sequence 33
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SQL alter system switch logfile;
SQL archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /home/oracle/arch_orcl
Oldest online log sequence 32
Next log sequence to archive 34
Current log sequence 34
192.168.1.183
SQL archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /home/oracle/arch_db01
Oldest online log sequence 32
Next log sequence to archive 0
Current log sequence 34
2 、最大性能模式--切换到--最大高可用 (默认是最大性能模式---MAXIMUM PERFORMANCE)。
192.168.1.181
SQL select DATABASE_ROLE,PROTECTION_MODE,PROTECTION_LEVEL from v$database;
DATABASE_ROLE PROTECTION_MODE PROTECTION_LEVEL
---------------- -------------------- --------------------
PRIMARY MAXIMUM PERFORMANCE MAXIMUM PERFORMANCE
SQL show parameter log_archive_dest_2
NAME TYPE VALUE
------------------------------------ ----------- ---------------------------
log_archive_dest_2 string service=db_db01 LGWR ASYNC val
id_for=(online_logfiles,primar
y_roles) db_unique_name=db01
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SQL shutdown immediate
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SQL alter database recover managed standby database cancel;
SQL shutdown immediate
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SQL startup mount;
SQL alter database set standby database to maximize availability;
SQL alter system set log_archive_dest_2='service=db_db01 LGWR SYNC valid_for=(online_logfiles,primary_roles) db_unique_name=db01' scope=spfile;
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SQL startup nomount
SQL alter database mount standby database;
SQL alter system set log_archive_dest_2='service=db_orcl LGWR SYNC valid_for=(online_logfiles,primary_roles) db_unique_name=orcl' scope=spfile;
SQL shutdown immediate
SQL startup nomount
SQL alter database mount standby database;
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SQL startup
SQL col dest_name for a25
SQL select dest_name,status from v$archive_dest_status;
DEST_NAME STATUS
------------------------- ---------
LOG_ARCHIVE_DEST_1 VALID
LOG_ARCHIVE_DEST_2 VALID
SQL show parameter log_archive_dest_2
NAME TYPE VALUE
------------------------------------ ----------- ---------------------------
log_archive_dest_2 string service=db_db01 LGWR SYNC vali
d_for=(online_logfiles,primary
_roles) db_unique_name=db01
SQL select database_role,protection_level,protection_mode from v$database;
DATABASE_ROLE PROTECTION_LEVEL PROTECTION_MODE
---------------- -------------------- --------------------
PRIMARY MAXIMUM AVAILABILITY MAXIMUM AVAILABILITY
SQL archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /home/oracle/arch_orcl
Oldest online log sequence 34
Next log sequence to archive 36
Current log sequence 36
192.168.1.183
SQL col dest_name for a25
SQL select dest_name,status from v$archive_dest_status;
DEST_NAME STATUS
------------------------- ---------
LOG_ARCHIVE_DEST_1 VALID
LOG_ARCHIVE_DEST_2 VALID
SQL show parameter log_archive_dest_2
NAME TYPE VALUE
------------------------------------ ----------- ---------------------------
log_archive_dest_2 string service=db_orcl LGWR SYNC vali
d_for=(online_logfiles,primary
_roles) db_unique_name=orcl
SQL select database_role,protection_level,protection_mode from v$database;
DATABASE_ROLE PROTECTION_LEVEL PROTECTION_MODE
---------------- -------------------- --------------------
PHYSICAL STANDBY MAXIMUM AVAILABILITY MAXIMUM AVAILABILITY
SQL archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /home/oracle/arch_db01
Oldest online log sequence 35
Next log sequence to archive 0
Current log sequence 36
192.168.1.181
SQL alter system switch logfile;
SQL archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /home/oracle/arch_orcl
Oldest online log sequence 35
Next log sequence to archive 37
Current log sequence 37
192.168.1.183
SQL archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /home/oracle/arch_db01
Oldest online log sequence 36
Next log sequence to archive 0
Current log sequence 37
3、最大高可用--切换到--最保护能模式，DG最大保护模式Maximum protection。
192.168.1.181
SQL shutdown immediate
192.168.1.183
SQL shutdown immediate
192.168.1.181
SQL alter database set standby database to maximize protection;
SQL shutdown immediate
192.168.1.183
SQL startup nomount
SQL alter database mount standby database;
192.168.1.181
SQL startup
SQL col dest_name for a25
SQL select dest_name,status from v$archive_dest_status;
DEST_NAME STATUS
------------------------- ---------
LOG_ARCHIVE_DEST_1 VALID
LOG_ARCHIVE_DEST_2 VALID
SQL show parameter log_archive_dest_2
NAME TYPE VALUE
------------------------------------ ----------- ---------------------------
log_archive_dest_2 string service=db_db01 LGWR SYNC vali
d_for=(online_logfiles,primary
_roles) db_unique_name=db01
SQL select database_role,protection_level,protection_mode from v$database;
DATABASE_ROLE PROTECTION_LEVEL PROTECTION_MODE
---------------- -------------------- --------------------
PRIMARY MAXIMUM PROTECTION MAXIMUM PROTECTION
SQL archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /home/oracle/arch_orcl
Oldest online log sequence 37
Next log sequence to archive 39
Current log sequence 39
192.168.1.183
SQL col dest_name for a25
SQL select dest_name,status from v$archive_dest_status;
DEST_NAME STATUS
------------------------- ---------
LOG_ARCHIVE_DEST_1 VALID
LOG_ARCHIVE_DEST_2 VALID
SQL show parameter log_archive_dest_2
NAME TYPE VALUE
------------------------------------ ----------- ---------------------------
log_archive_dest_2 string service=db_db01 LGWR SYNC vali
d_for=(online_logfiles,primary
_roles) db_unique_name=db01
SQL select database_role,protection_level,protection_mode from v$database;
DATABASE_ROLE PROTECTION_LEVEL PROTECTION_MODE
---------------- -------------------- --------------------
PRIMARY MAXIMUM PROTECTION MAXIMUM PROTECTION
SQL archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /home/oracle/arch_db01
Oldest online log sequence 37
Next log sequence to archive 0
Current log sequence 39
192.168.1.181
SQL alter system switch logfile;
SQL archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /home/oracle/arch_orcl
Oldest online log sequence 38
Next log sequence to archive 40
Current log sequence 40
192.168.1.183
SQL archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /home/oracle/arch_db01
Oldest online log sequence 37
Next log sequence to archive 0
Current log sequence 40
