在RAC环境中，如果你在没有启动节点的集群服务的情况下单实例启动数据库，将收到类似如下的报错：

[oracle@rhel1 u01]$ sql

SQL*Plus: Release 10.2.0.5.0 - Production on Tue Apr 2 15:00:27 2013

Connected to an idle instance.

SQL> startup nomount

ORA-29702: error occurred in Cluster Group Service operation

数据库实例无法启动，要求先启动CGS服务，原因可以大概从下面这篇METALINK文章中知道：
AIX: ORA-29702 When Creating A Single Instance Database In A Clustered Environment [ID 198901.1]
修改时间:2010-10-19

类型:PROBLEM

状态:PUBLISHED

优先级:2

Problem Description
-------------------

When starting up a single instance on aan AIX clustered environment, the 
following error is reported:

Error:	ORA-29702
Text:	error occurred in Cluster Group Service operation 
---------------------------------------------------------------------------
Cause:	An unexpected error occurred while performing a CGS operation. 
Action:	Verify that the LMON process is still active. Also, check the Oracle 
	LMON trace files for errors.


Solution Description
--------------------

1) reinstall Oracle software by de-selecting Oracle Parallel Server option.
2) deinstall Oracle Parallel Server option and relink oracle kernel.
   
   It is possible to do it manually by entering the following commands:

   cd ORACLE_HOME/rdbms/lib
   make -f ins_rdbms.mk no_parropt or make -f ins_rdbms.mk ops_off
   make -f ins_rdbms.mk install
 

Explanation
-----------

High Availability Group Services (HAGS) is not configured .
When creating a single instance database in a clustered environment, if you 
have a cluster software installed, then OUI detects it and installs Oracle 
Parallel Server option by default. 


Additional Search Words
-----------------------

ORA-29702, startup, start up, create

从上面的文章，大概知道是由于Oracle Database软件中的Oracle Parallel Server option引起的问题，解决办法是执行相关命令卸载Oracle Parallel Server Option，然后重新编译Oracle内核。
这里用一个简单的办法，在RAC的节点上新安装一个单机版的Oracle Database软件，用它来单实例启动数据库，下面是例子：

[root@rhel1 bin]# su - oracle

[oracle@rhel1 ~]$ echo $ORACLE_HOME

/u01/app/oracle/db_2

这是新安装的单机版Oracle软件HOME。

[oracle@rhel1 ~]$ sql

SQL*Plus: Release 10.2.0.5.0 - Production on Tue Apr 2 15:39:37 2013

Connected to an idle instance.

SQL> startup nomount

ORACLE instance started.

Total System Global Area 432013312 bytes

Fixed Size 2096824 bytes

Variable Size 125829448 bytes

Database Buffers 297795584 bytes

Redo Buffers 6291456 bytes

启动实例前，先去掉和RAC相关的参数设置。

SQL> show parameter control

NAME TYPE

------------------------------------ ----------------------

VALUE

------------------------------

control_file_record_keep_time integer

7

control_files string

/u01/ractest/control01.ctl, /u

01/ractest/control02.ctl, /u01

/ractest/control03.ctl

SQL> alter database mount;

Database altered.

注意对数据文件和在线Redo文件位置的调整。

SQL> alter database open;

Database altered.

数据库正常启动。

从这个例子可以猜想，如果将参数文件、控制文件、日志文件和数据文件拷贝到其他单机版数据库环境中也能正常的启动。

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RAC环境单实例启动数据库收到ORA-29702报错