How to change single-instance database to RAC（10g）

背景：新增一台服务器，将一生产系统升级为rac，要求不影响业务
需要在原生产的单机环境上安装rac
环境：redhat 5.4 oracle10.2.0.4
疑问：如何将单机升级为rac，能否在旧有的单机运行时安装rac，即两者能否共存
=== ODM Answer ===
Dear customer, you can install the new cluster ware and database software when the old database was running.
the main steps to be finished would be the following:

1. Installed the new cluster ware and database software on new oracle home. When you install the rac enabled database software, pls select 'install software only'.
Then upgrade the new installed binaries to 10.2.0.4

2. create disk groups for asm, this can be done with dbca.

3. change the bash_profile to make sure the oracle user use new binary by set variable oracle_home, ora_crs_home and others.

4. make a full backup for the old database with rman.

5. restore the backup set to asm.

6. add redo thread and undo tablespace for new instances , for instance, this is a 2 nodes rac system, you need to add redo thread and undo tablespace for
instance 2

7. switch your application to the new database.

8. remove old database and binary with dbca and OUI.

Comment: Pls check the note 747457.1 : How to Convert 10g Single-Instance database to 10g RAC using Manual Conversion procedure
For detail steps about the part of change database. One more thing, the note use cluster file system for the new rac enabled database, pls
change the cluster file system path to asm diskgroup name to suit your case.

实施步骤：
1. 第一个晚上申请停机，做准备工作，包括修改hostname、hosts文件、新的环境变量、检查系统包、划分存储等。
2.第二天工作时间进行rac安装、数据库的创建。
3.第二个晚上申请停机，迁移数据。修改应用、dblink到rac上。
遇到的问题：
1.提前修改oracle安装目录：/etc/oraInst.loc，否则，哪怕指定了新的ORACLE_BASE、ORACLE_HOME，新的软件也会安装在原目录中。
2.注意新rac的监听不要与原来的冲突。