Three ways to startup an ASM instance on a server

Before 11gR2 there was only one way to startup an ASM instance [SQLPLUS].
In 11gR2 Oracle has added a startup/shutdown  functionality in the ASMCMD line interface and introduced a new GUI ASMCA.
The GUI willl detect by startup if there is an ASM instance operational or not. If not then it prompt to start an ASM instance.

The Three methods:

• SQLPLUS with sysasm attribute

1 2	sqlplus / as asmdba startup

• ASMCMD

1	asmcmd> startup

• ASMCA

ASMCMD help in release 11gR2

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ASMCMD> help         asmcmd [-vV] [-a ] [-p] [command]         The environment variables ORACLE_HOME and ORACLE_SID determine the         instance to which the program connects, and ASMCMD establishes a         bequeath connection to it, in the same manner as a SQLPLUS / AS         SYSASM.  The user must be a member of the OSASM group.         Specifying the -V option prints the asmcmd version number and         exits immediately.         Specifying the -v option prints extra information that can help         advanced users diagnose problems.         Specify the -a option to choose the type of connection. There are         only two possibilities: connecting as SYSASM or as SYSDBA.         The default value if this option is unspecified is SYSASM.         Specifying the -p option allows the current directory to be displayed         in the command prompt, like so:         ASMCMD [+DATA/ORCL/CONTROLFILE] >         [command] specifies one of the following commands, along with its         parameters.         Type "help [command]" to get help on a specific ASMCMD command.         commands:         --------         md_backup, md_restore         lsattr, setattr         cd, cp, du, find, help, ls, lsct, lsdg, lsof, mkalias         mkdir, pwd, rm, rmalias         chdg, chkdg, dropdg, iostat, lsdsk, lsod, mkdg, mount         offline, online, rebal, remap, umount         dsget, dsset, lsop, shutdown, spbackup, spcopy, spget         spmove, spset, startup         chtmpl, lstmpl, mktmpl, rmtmpl         chgrp, chmod, chown, groups, grpmod, lsgrp, lspwusr, lsusr         mkgrp, mkusr, orapwusr, passwd, rmgrp, rmusr         volcreate, voldelete, voldisable, volenable, volinfo         volresize, volset, volstat ASMCMD>

ASMCMD help before 11gR2

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ASMCMD> help         asmcmd [-v] [-a ] [-p] [command]         The environment variables ORACLE_HOME and ORACLE_SID determine the         instance to which the program connects, and ASMCMD establishes a         bequeath connection to it, in the same manner as a SQLPLUS / AS         SYSDBA.  The user must be a member of the SYSDBA group.         Specifying the -v option prints the asmcmd version number and         exits immediately.         Specify the -a option to choose the type of connection. There are         only two possibilities: connecting as "sysasm" or as "sysdba".         The default value if this option is unspecified is "sysasm".         Specifying the -p option allows the current directory to be displayed         in the command prompt, like so:         ASMCMD [+DATAFILE/ORCL/CONTROLFILE] >         [command] specifies one of the following commands, along with its         parameters.         Type "help [command]" to get help on a specific ASMCMD command.         commands:         --------         help         cd         cp         du         find         ls         lsct         lsdg         mkalias         mkdir         pwd         rm         rmalias         md_backup         md_restore         lsdsk         remap ASMCMD>