Por algumas vezes, quando adicionando mais grupos em um RAC aconteceu o erro:

ORA-01102: cannot mount database in EXCLUSIVE mode

Assim, consegui detectar que em alguns casos simplesmente efetuando o boot e em outros casos resolvendo somente colocando novamente em modo de CLUSTER atraves dos parametros abaixo:
cluster_database boolean
TRUE
cluster_database_instances integer
2

veja o erro abaixo:

Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 – Production
With the Partitioning, Real Application Clusters, OLAP and Data Mining options

SQL> show parameter cluster

NAME TYPE
———————————— ———————————
VALUE
——————————
cluster_database boolean
FALSE
cluster_database_instances integer
1
cluster_interconnects string

SQL> alter system set cluster_database=TRUE scope=spfile sid=’*’;

System altered.

SQL> alter system set cluster_database_instances=2 scope=spfile sid=’*’;

System altered.

SQL> shutdown immediate

Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> SQL> SQL>
SQL>
SQL> startup
ORACLE instance started.

Total System Global Area 583008256 bytes
Fixed Size 1220676 bytes
Variable Size 201330620 bytes
Database Buffers 373293056 bytes
Redo Buffers 7163904 bytes
Database mounted.
Database opened.
SQL>

ora.eg7086.vip application ONLINE ONLINE eg7086
[oracle@eg7038 ~]$ crs_stat -t
Name Type Target State Host
————————————————————
ora….B1.inst application ONLINE OFFLINE
ora….B2.inst application ONLINE ONLINE eg7086
ora.RDBB.db application ONLINE ONLINE eg7038
ora….SM1.asm application ONLINE ONLINE eg7038
ora….38.lsnr application ONLINE ONLINE eg7038
ora.eg7038.gsd application ONLINE ONLINE eg7038
ora.eg7038.ons application ONLINE ONLINE eg7038
ora.eg7038.vip application ONLINE ONLINE eg7038
ora….SM2.asm application ONLINE ONLINE eg7086
ora….86.lsnr application ONLINE ONLINE eg7086
ora.eg7086.gsd application ONLINE ONLINE eg7086
ora.eg7086.ons application ONLINE ONLINE eg7086
ora.eg7086.vip application ONLINE ONLINE eg7086
[oracle@eg7038 ~]$ ps -ef |grep pmon
oracle 31627 1 0 20:39 ? 00:00:00 asm_pmon_+ASM1
oracle 10191 1 2 20:46 ? 00:00:00 ora_pmon_RDBB1
oracle 10484 27876 0 20:46 pts/2 00:00:00 grep pmon
[oracle@eg7038 ~]$ sqlplus / as sysdba

SQL*Plus: Release 10.2.0.1.0 – Production on Tue Oct 6 20:46:53 2009

Copyright (c) 1982, 2005, Oracle. All rights reserved.

Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 – Production
With the Partitioning, Real Application Clusters, OLAP and Data Mining options

SQL> show parameter thread

NAME TYPE
———————————— ———————————
VALUE
——————————
parallel_threads_per_cpu integer
2
thread integer
1
SQL> show parameter cluster

NAME TYPE
———————————— ———————————
VALUE
——————————
cluster_database boolean
FALSE
cluster_database_instances integer
1
cluster_interconnects string

SQL> alter system set cluster_database=TRUE scope=spfile sid=’*’;

System altered.

SQL> alter database mount;
alter database mount
*
ERROR at line 1:
ORA-01102: cannot mount database in EXCLUSIVE mode

SQL> alter system set cluster_database_instances=2 scope=spfile;

System altered.

SQL> alter database mount;
alter database mount
*
ERROR at line 1:
ORA-01102: cannot mount database in EXCLUSIVE mode

SQL> shutdown immediate;
ORA-01507: database not mounted

ORACLE instance shut down.
SQL> startup
ORA-29707: inconsistent value 2 for initialization parameter cluster_database_instances with other instances
SQL> alter system set cluster_database_instances=2 scope=spfile sid=’*’;
alter system set cluster_database_instances=2 scope=spfile sid=’*’
*
ERROR at line 1:
ORA-01034: ORACLE not available

SQL> startup nomount;
ORA-29707: inconsistent value 2 for initialization parameter cluster_database_instances with other instances
SQL> shutdown immediate;
ORA-01012: not logged on
SQL> conn / as sysdba
Connected to an idle instance.
SQL> startup
ORA-29707: inconsistent value 2 for initialization parameter cluster_database_instances with other instances
SQL> conn / as sysdba
Connected to an idle instance.
SQL> startup
ORACLE instance started.

Total System Global Area 583008256 bytes
Fixed Size 1220676 bytes
Variable Size 222302140 bytes
Database Buffers 352321536 bytes
Redo Buffers 7163904 bytes
Database mounted.
Database opened.
SQL>