This is more a note to myself in case I’ll encounter a similar environment. But maybe it helps others – at least my search results weren’t suitable to Windows in the first place.

Issue

C:\> set ORACLE_HOME=C:\path\to\grid\home
C:\> set ORACLE_SID=+ASM1
C:\> asmcmd
connected to an idle instance.

Environment

• Windows 2012R2
• Oracle Grid Infrastructure 12.1.0.1
• 2 Nodes, both ASM instances running.

Further Diagnosis

C:\> sqlplus / as sysasm
...
ORA-01017: invalid username/password; logon denied.

But as sysdba:

C:\> sqlplus / as sysdba
...
connected.
SQL>

As asmcmd does nothing else than a connection as SYSASM, it looks like asmcmd’s error message is misleading. That would not be something completely new with Oracle tools…

Solution

For whatever reason, the Grid Home User was not (anymore?) part of the Windows user group “ORA_ASMADMIN”.

Adding the user to this group on all nodes and logging off and on again resolved this issue.