在集群中的初始配置SCAN只有一个IP，需要再增加两个IP。增加过程记录如下：

1. 查看原SCAN配置

# srvctl config scan
SCAN name: ora-node-scan, Network: 1
Subnet IPv4: 10.1.7.0/255.255.255.0/eth0, static
Subnet IPv6: 
SCAN 0 IPv4 VIP: 10.1.7.240
SCAN VIP is enabled.
SCAN VIP is individually enabled on nodes: 
SCAN VIP is individually disabled on nodes: 

# srvctl config scan_listener
SCAN Listener LISTENER_SCAN1 exists. Port: TCP:1521
Registration invited nodes: 
Registration invited subnets: 
SCAN Listener is enabled.
SCAN Listener is individually enabled on nodes: 
SCAN Listener is individually disabled on nodes:

2. 在hosts文件中，增加IP配置

# vim /etc/hosts
# 将下面最后2行添加到文件中
10.1.7.240 rac-scan
10.1.7.239 rac-scan
10.1.7.238 rac-scan

注意：其它节点该文件同步更新。

3. 停止SCAN服务和监听

# srvctl stop scan_listener
# srvctl stop scan
# srvctl status scan_listener
SCAN Listener LISTENER_SCAN1 is enabled
SCAN listener LISTENER_SCAN1 is not running

4. 修改SCAN信息，增加SCAN监听的IP

# srvctl modify scan -n rac-scan
# srvctl modify scan_listener -u

# srvctl status scan_listener
SCAN Listener LISTENER_SCAN1 is enabled
SCAN listener LISTENER_SCAN1 is not running
SCAN Listener LISTENER_SCAN2 is enabled
SCAN listener LISTENER_SCAN2 is not running
SCAN Listener LISTENER_SCAN3 is enabled
SCAN listener LISTENER_SCAN3 is not running

5. 重启SCAN服务和监听

# srvctl start scan
# srvctl start scan_listener

也可以直接启动监听，会自动启动scan的。
检查增加的结果和状态。

# srvctl config scan
SCAN name: rac-scan, Network: 1
Subnet IPv4: 10.1.7.0/255.255.255.0/eth0, static
Subnet IPv6: 
SCAN 0 IPv4 VIP: 10.1.7.240
SCAN VIP is enabled.
SCAN VIP is individually enabled on nodes: 
SCAN VIP is individually disabled on nodes: 
SCAN 1 IPv4 VIP: 10.1.7.239
SCAN VIP is enabled.
SCAN VIP is individually enabled on nodes: 
SCAN VIP is individually disabled on nodes: 
SCAN 2 IPv4 VIP: 10.1.7.238
SCAN VIP is enabled.
SCAN VIP is individually enabled on nodes: 
SCAN VIP is individually disabled on nodes: 

# srvctl config scan_listener
SCAN Listener LISTENER_SCAN1 exists. Port: TCP:1521
Registration invited nodes: 
Registration invited subnets: 
SCAN Listener is enabled.
SCAN Listener is individually enabled on nodes: 
SCAN Listener is individually disabled on nodes: 
SCAN Listener LISTENER_SCAN2 exists. Port: TCP:1521
Registration invited nodes: 
Registration invited subnets: 
SCAN Listener is enabled.
SCAN Listener is individually enabled on nodes: 
SCAN Listener is individually disabled on nodes: 
SCAN Listener LISTENER_SCAN3 exists. Port: TCP:1521
Registration invited nodes: 
Registration invited subnets: 
SCAN Listener is enabled.
SCAN Listener is individually enabled on nodes: 
SCAN Listener is individually disabled on nodes:

# srvctl status scan
SCAN VIP scan1 is enabled
SCAN VIP scan1 is running on node ora-node3
SCAN VIP scan2 is enabled
SCAN VIP scan2 is running on node ora-node2
SCAN VIP scan3 is enabled
SCAN VIP scan3 is running on node ora-node1

# srvctl status scan_listener
SCAN Listener LISTENER_SCAN1 is enabled
SCAN listener LISTENER_SCAN1 is running on node ora-node3
SCAN Listener LISTENER_SCAN2 is enabled
SCAN listener LISTENER_SCAN2 is running on node ora-node2
SCAN Listener LISTENER_SCAN3 is enabled
SCAN listener LISTENER_SCAN3 is running on node ora-node1

该过程在12c上操作，11g适用。

6. 客户端如何使用SCAN连接数据库

集群环境安装完成后，客户端是不能使用SCAN连接数据库的，报出错误，如下：

连接错误

需要进行如下配置。

SQL> show parameter local_listener

NAME                     TYPE    VALUE
------------------------------------ ----------- ------------------------------
local_listener               string   (ADDRESS=(PROTOCOL=TCP)(HOST=
                         10.1.7.88)(PORT=1521))

SQL> alter system set local_listener='(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=rac-scan)(PORT=1521))))' scope=both;

System altered.

在客户端将如下信息加入hosts文件（windows和linux的位置不同）

10.1.7.240 rac-scan
10.1.7.239 rac-scan
10.1.7.238 rac-scan

现在再使用客户端，通过SCAN就可以连接数据库了。

C:\Users\Administrator>sqlplus test/oracle@rac-scan:1521/MKDB

SQL*Plus: Release 11.2.0.4.0 Production on Fri Jun 2 14:23:31 2017

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


Connected to:
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
With the Partitioning, Real Application Clusters, Automatic Storage Management,
OLAP,
Advanced Analytics and Real Application Testing options

SQL> select * from dual;

D
-
X

SQL> select * from tab1;

COL1
----------
SECOND