How to change ARCHIVE_LOG_FORMAT ?

server1[rac1]_oracle> sqlplus
SQL*Plus: Release 11.2.0.2.0 Production on Wed Sep 7 04:15:00 2011
Copyright (c) 1982, 2010, Oracle. All rights reserved.
Enter user-name: / as sysdba
Connected to:Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit ProductionWith the Partitioning, Real Application Clusters, Automatic Storage Management, OLAP,Data Mining and Real Application Testing options
SQL> show parameter format
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------log_archive_format string %t_%s_%r.dbf
nls_date_format string
nls_time_format string
nls_time_tz_format string
nls_timestamp_format string
nls_timestamp_tz_format string
permit_92_wrap_format boolean TRUE
star_transformation_enabled string FALSE

SQL> show parameter spfile

NAME TYPE VALUE
-------------------------------------------------------------------

spfile string +RAC_VG/rac/spfilerac.ora

SQL> create pfile='$ORACLE_HOME/dbs/initrac_new.ora' from spfile='+RAC_VG/rac/spfilerac.ora';
File created.

SQL> exitDisconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit ProductionWith the Partitioning, Real Application Clusters, Automatic Storage Management, OLAP,Data Mining and Real Application Testing options

server1[rac1]_oracle> cd $ORACLE_HOME/dbs/

server1[rac1]_oracle> ls -ltr initrac_new.ora

server1[rac1]_oracle> srvctl stop database -d rac -o immediate -f

server1[rac1]_oracle> srvctl status database -d rac

Instance rac1 is not running on node server1
Instance rac2 is not running on node server2

server1[rac1]_oracle> vi initrac_new.ora

*.log_archive_format='log_%t_%s_%r.arc'

"initrac_new.ora" 44L, 1561C written

server1[rac1]_oracle> sqlplus
SQL*Plus: Release 11.2.0.2.0 Production on Wed Sep 7 04:28:11 2011
Copyright (c) 1982, 2010, Oracle. All rights reserved.
Enter user-name: / as sysdba
Connected to an idle instance.

SQL> startup nomount pfile='$ORACLE_HOME/dbs/initrac_new.ora'

ORACLE instance started.
Total System Global Area 2.4185E+10 bytes
Fixed Size 2280880 bytes
Variable Size 4395631184 bytes
Database Buffers 1.9780E+10 bytes
Redo Buffers 7221248 bytes

SQL> create spfile='+RAC_VG/rac/spfilerac.ora' from pfile='$ORACLE_HOME/dbs/initrac_new.ora';
File created.

SQL> shutdown immediate
ORA-01507: database not mounted
ORACLE instance shut down.

SQL> exit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit ProductionWith the Partitioning, Real Application Clusters, OLAP, Data Miningand Real Application Testing options

server1[rac1]_oracle> srvctl start database -d rac

server1[rac1]_oracle> sqlplus
SQL*Plus: Release 11.2.0.2.0 Production on Wed Sep 7 04:31:25 2011
Copyright (c) 1982, 2010, Oracle. All rights reserved.
Enter user-name: / as sysdba
Connected to:Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit ProductionWith the Partitioning, Real Application Clusters, Automatic Storage Management, OLAP,Data Mining and Real Application Testing options

SQL> show parameter format

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------

log_archive_format string log_%t_%s_%r.arc
nls_date_format string
nls_time_format string
nls_time_tz_format string
nls_timestamp_format string
nls_timestamp_tz_format string
permit_92_wrap_format boolean TRUE
star_transformation_enabled string FALSE