时间：2021-07-01 10:21:17 帮助过：23人阅读
一、SID、ORACLE_SID：
SID的全称为site identifier，Oracle_SID则为Oracle site identifier.
下面引用Tom(Thomas Kyte)的一段话来解释Oracle_SID
If you’re unfamiliar with the term SID or ORACLE_SID, a full definition is called for. The SID is a site identifier. It and ORACLE_HOME (where the Oracle software is installed) are hashed together in UNIX to create a unique key name for attaching an SGA. If your ORACLE_SID or ORACLE_HOME is not set correctly, you’ll get the ORACLE NOT AVAILABLE error, since you can’t attach to a shared memory segment that is identified by this unique key. On Windows, shared memory isn’t used in the same fashion as UNIX, but the SID is still important. You can have more than one database on the same ORACLE_HOME, so you need a way to uniquely identify each one, along with their configuration files.
即：在Unix系统中，SID和ORACLE_HOME在一起哈希后得到一个唯一的值作为SGA的key。
当oracle实例启动时，在操作系统上的fork进程则根据Oracle_SID来创建相关后台进程。
Oracle 11g 支持Oracle_SID的长度为12位，db_name的长度为8位
作用：
用于区别同一台主机上不同的Oracle实例
决定实例所启动后台进程的名称。(实例由SGA和后台进程组成)
决定了参数文件的名称。如spfile<ORACLE_SID>.ora,init<ORACLE_SID>.ora
决定后台进程产生的相关跟踪文件、日志文件等。
如alert_<ORACLE_SID>.log,<ORACLE_SID>_arc1_<spid>.trc,<SID>_ora_<SPID>.trc
同一主机上不同的$ORACLE_HOME，可以创建相同的ORACLE_SID
由此可以得出
ORACLE_HOME相同时，可以使用不同的ORACLE_SID
ORACLE_HOME不同时，可以使用相同的ORACLE_SID
[oracle@robinson ~]$ export ORACLE_SID=orcl --设定ORACLE_SID为orcl
[oracle@robinson ~]$ sqlplus / as sysdba;
SQL*Plus: Release 10.2.0.1.0 - Production on Wed Sep 1 09:46:36 2010
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to an idle instance.
SQL> startup nomount;
ORACLE instance started.
Total System Global Area 469762048 bytes
Fixed Size 1220048 bytes
Variable Size 117441072 bytes
Database Buffers 348127232 bytes
Redo Buffers 2973696 bytes
SQL> ho ps -ef | grep oracle --ORACLE_SID参与了后台进程命名
oracle 3272 1 0 09:46 ? 00:00:00 ora_pmon_orcl
oracle 3274 1 0 09:46 ? 00:00:00 ora_psp0_orcl
oracle 3276 1 1 09:46 ? 00:00:00 ora_mman_orcl
oracle 3278 1 0 09:46 ? 00:00:00 ora_dbw0_orcl
oracle 3280 1 0 09:46 ? 00:00:00 ora_lgwr_orcl
oracle 3282 1 0 09:46 ? 00:00:00 ora_ckpt_orcl
oracle 3284 1 0 09:46 ? 00:00:00 ora_smon_orcl
---------............部分结果省略.............. --------------
二、INSTANCE_NAME
用于标识数据库实例的名称，缺省值通常为ORACLE_SID
用于和操作系统之间联系，根据实例名产生的响应的实例来取得与数据库的交互
初始化参数中INSTANCE_NAME与ORACLE_SID可以不同
不同的实例可以拥有相同的INSTANCE_NAME，只要ORACLE_SID不同，则与ORACLE_HOME哈希可以得到不同的值
INSTANCE_NAME可以用于向监听器动态注册
[oracle@robinson ~]$ cp $ORACLE_HOME/dbs/initorcl.ora $ORACLE_HOME/dbs/initscott.ora
[oracle@robinson ~]$ export ORACLE_SID=scott --设定ORACLE_SID为scott
[oracle@robinson ~]$ env | grep ORA
ORACLE_SID=scott
ORACLE_BASE=/u01/app/oracle
ORACLE_HOME=/u01/app/oracle/10g
[oracle@robinson ~]$ sqlplus / as sysdba
SQL*Plus: Release 10.2.0.1.0 - Production on Wed Sep 1 10:04:59 2010
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to an idle instance.
SQL> startup nomount; --启动实例scott
ORACLE instance started.
Total System Global Area 469762048 bytes
Fixed Size 1220048 bytes
Variable Size 134218288 bytes
Database Buffers 331350016 bytes
Redo Buffers 2973696 bytes
SQL> show parameter instance_name;
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
instance_name string scott
SQL> ho ps -ef | grep scott --可以看到后台以scott命名的进程
oracle 3489 1 0 10:05 ? 00:00:00 ora_pmon_scott
oracle 3491 1 0 10:05 ? 00:00:00 ora_psp0_scott
oracle 3493 1 0 10:05 ? 00:00:00 ora_mman_scott
oracle 3495 1 0 10:05 ? 00:00:00 ora_dbw0_scott
oracle 3497 1 0 10:05 ? 00:00:00 ora_lgwr_scott
oracle 3499 1 0 10:05 ? 00:00:00 ora_ckpt_scott
---------............部分结果省略.............. --------------
SQL> ho ps -ef | grep ora --此时可以看到后台启动了orcl和scott两个实例
oracle 3445 1 0 10:01 ? 00:00:00 ora_pmon_orcl
oracle 3447 1 0 10:01 ? 00:00:00 ora_psp0_orcl
oracle 3449 1 0 10:01 ? 00:00:00 ora_mman_orcl
oracle 3451 1 0 10:01 ? 00:00:00 ora_dbw0_orcl
oracle 3453 1 0 10:01 ? 00:00:00 ora_lgwr_orcl
oracle 3455 1 0 10:01 ? 00:00:00 ora_ckpt_orcl
oracle 3457 1 0 10:01 ? 00:00:00 ora_smon_orcl
oracle 3497 1 0 10:05 ? 00:00:00 ora_lgwr_scott
oracle 3499 1 0 10:05 ? 00:00:00 ora_ckpt_scott
oracle 3501 1 0 10:05 ? 00:00:00 ora_smon_scott
oracle 3503 1 0 10:05 ? 00:00:00 ora_reco_scott
oracle 3505 1 0 10:05 ? 00:00:00 ora_cjq0_scott
oracle 3507 1 0 10:05 ? 00:00:00 ora_mmon_scott
---------............部分结果省略.............. --------------
SQL>select*from dual;
ADDR INDX INST_ID D
-------- ---------- ---------- -
0C4B2FD4 0 1 X
--用于向监听器动态注册
SQL> ho lsnrctl status
LSNRCTL for Linux: Version 10.2.0.1.0 - Production on 01-SEP-2010 12:30:13
--------------------------部分省略---------------------------------------
Listener Parameter File /u01/app/oracle/10g/network/admin/listener.ora
Listener Log File /u01/app/oracle/10g/network/log/listener.log
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=robinson.com)(PORT=1521)))
Services Summary...
Service "PLSExtProc" has 1 instance(s).--服务名PLSExtProc及实例名PLSExtProc
Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service...
Service "orcl" has 1 instance(s).
Instance "orcl", status READY, has 1 handler(s) for this service...
Service "orclXDB" has 1 instance(s). --服务名orcl_XDB，实例名为orcl
Instance "orcl", status READY, has 1 handler(s) for this service...
Service "orcl_XPT" has 1 instance(s).--服务名orcl_XPT，实例名为orcl
Instance "orcl", status READY, has 1 handler(s) for this service...
The command completed successfully
三、DB_NAME
数据库的唯一标识，是一个不超过8个字符的文本串
在创建数据库时定义，被记录在数据文件、控制文件和日志文件当中。
用于实例与数据库的挂接，通常缺省的情况下，INSTANCE_NAME与