oracle安装可以参考：https://www.jianshu.com/p/b4200e721bfd
centos下载：http://mirrors.163.com/centos/
oracle下载：https://www.oracle.com/technetwork/database/enterprise-edition/downloads/112010-linx8664soft-100572.html
#查看service_name
show parameter service_names;
1.修改用户密码
sqlplus / as sysdba
查看所有用户信息
SQL> select username,password from dba_users;
修改密码
SQL> alter user system identified by 123456;
2.新增用户
SQL> create user test identified by 123456;
否被会报错： [ORA-01045: user lacks CREATE SESSION privilege; logon denied(10.2.0.5)
SQL> grant create session to test;
#给用户赋予权限，及表空间权限
grant create any table to test;
ALTER USER test quota unlimited on users;
3.error:ORA-01034: ORACLE not available Process ID: 0 Session ID: 0 Serial number: 0
(1)方法1
ps -ef | grep smon | awk '{print $2}'|xargs kill -9
sqlplus / as sysdba
startup
然后再：
select 1 from dual；
发现 ok
（2）方法2
查看：
echo $ORACLE_SID
lsnrctl status
查看这两个ORACLE_SID是否一致
LSNRCTL for Linux: Version 11.2.0.1.0 - Production on 13-SEP-2018 15:06:10
Copyright (c) 1991, 2009, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC1521)))
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for Linux: Version 11.2.0.1.0 - Production
Start Date 13-SEP-2018 14:55:18
Uptime 0 days 0 hr. 10 min. 52 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /data/app/oracle/product/11.2.0/db_1/network/admin/listener.ora
Listener Log File /data/app/oracle/diag/tnslsnr/centos/listener/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=centos)(PORT=1521)))
Services Summary...
Service "orcl11g.us.oracle.com" has 1 instance(s).
Instance "orcl11g", status READY, has 1 handler(s) for this service...
Service "orcl11gXDB.us.oracle.com" has 1 instance(s).
Instance "orcl11g", status READY, has 1 handler(s) for this service...
The command completed successfully
发现不一致：
Instance "orcl11g", status READY, has 1 handler(s) for this service...
echo $ORACLE_SID
输出:orcl
则去
vi /data/app/oracle/product/11.2.0/db_1/bin/dbstart
查看：
# Starts a Database Instance
startinst() {
# Called programs use same database ID
export ORACLE_SID
发现 ORACLE_SID直接export 并未初始化
则在export加一句 ORACLE_SID = orcl(视情况而定)
然后reboot 之后发现：
select 1 from dual;
ok
