For a brief introduction to the environment variable ORACLE_SID, the environment variable oracle_sid

For a brief introduction to the environment variable ORACLE_SID, the environment variable oracle_sid
[Oracle10g @ lixora ~] $ Export ORACLE_SID = 12323
[Oracle10g @ lixora ~] $! SQL
Sqlplus/as sysdba

SQL * Plus: Release 10.2.0.1.0-Production on Thu Nov 6 02:24:04 2014

Copyright (c) 1982,200 5, Oracle. All rights reserved.

Connected to an idle instance.


SQL> startup
ORA-01078: failure in processing system parameters
LRM-00109: cocould not open parameter file '/u02/app/oracle/product/10.2.0/db_1/dbs/init12323.ora'

SQL>

First, set a random oracle_sid, log on to sqlplus, and then click "startup". oracle will install the oracle database in the order of $ ORACLE_HOME/dbs according to the environment variable oracle_sid.

Spfile12323.ora --"

Pfile. ora --"

Init12323.ora --"

Init. ora --"

Find the oracle initialization parameter file. Since it is the initialization parameter file, of course it is to configure something for oracle -- share the memory, background process

After a normal instance is initialized, the following information is displayed:

1. Shared Memory segments:

[Oracle10g @ lixora ~] $ Ipcs-


------ Shared Memory Segments --------
Key shmid owner perms bytes nattch status
0x00000000 2785281 root 644 80 2
0x00000000 2818050 root 644 16384 2
0x00000000 2850819 root 644 280 2
0xa1728964 3244037 oracle10g 640 216006656 20--- Oracle10g is a user of oracle software.


------ Semaphore Arrays --------
Key semid owner perms nsems
0x17ee0b04 1441793 oracle10g 640 154


------ Message Queues --------
Key msqid owner perms used-bytes messages

When a pfile is specified, an instance can be started:

[Oracle10g @ lixora dbs] $ ipcs-


------ Shared Memory Segments --------
Key shmid owner perms bytes nattch status
0x00000000 2785281 root 644 80 2
0x00000000 2818050 root 644 16384 2
0x00000000 2850819 root 644 280 2
0xa1728964 3244037 oracle10g 640 216006656 20
0xb4c20568 3276806 oracle10g 640 169869312 10


------ Semaphore Arrays --------
Key semid owner perms nsems
0x17ee0b04 1441793 oracle10g 640 154
0x65dc2878 1572866 oracle10g 640 44


------ Message Queues --------
Key msqid owner perms used-bytes messages


[Oracle10g @ lixora dbs] $ ps-ef | grep smon
54322 17981 1 0 Nov05? 00:00:02 ora_smon_ora10g
54322 22649 1 0? 00:00:00 ora_smon_12323
54322 22660 22299 0 00:00:00 pts/3 grep smon
[Oracle10g @ lixora dbs] $

Here again, we emphasize that oracle_sid and db_name of oracle are two different things. ORALCE_SID is only an instance that uniquely identifies oracle )!