Create ASM instance

$ export ORACLE_BASE=/u01/app/oracle
$ export ORACLE_HOME=$ORACLE_BASE/product/11.2.0/grid
$ orapwd file=$ORACLE_HOME/dbs/orapwd+ASM password= entries=20
$ mkdir -p $ORACLE_BASE/admin/+ASM
$ cd $ORACLE_BASE/admin/+ASM

Create init+ASM.ora file.

+ASM.__large_pool_size=20971520
+ASM.__shared_pool_size=515899392
##+ASM.asm_diskgroups='DATADG','FRADG'  #Manual Dismount
*.asm_power_limit=1
*.diagnostic_dest='/u01/app/oracle'
*.instance_type='asm'
*.large_pool_size=12M
*.remote_login_passwordfile='EXCLUSIVE'
$ export ORACLE_SID=+ASM
$ sqlplus / as sysasm

SQL> startup nomount pfile='$ORACLE_HOME/dbs/init+ASM'