Oracle 11g R2 -- ORA-15477: cannot communicate with the volume driver

Problem

When you try to enable a volume on a diskgroup you get error

SQL> alter diskgroup dg1 enable volume dg1_vol1;
alter diskgroup dg1 enable volume dg1_vol1
*
ERROR at line 1:
ORA-15032: not all alterations performed
ORA-15477: cannot communicate with the volume driver

Solution

ACFS driver is not loaded automatically after a system restart. 

Load ACFS driver manually.

C:\> %GRID_HOME%\BIN\acfsload start -s

ACFS-9391: Checking for existing ADVM/ACFS installation.
ACFS-9392: Validating ADVM/ACFS installation files for operating system.
ACFS-9393: Verifying ASM Administrator setup.
ACFS-9308: Loading installed ADVM/ACFS drivers.
ACFS-9154: Loading 'oracle oks' driver.
ACFS-9154: Loading 'oracle advm' driver.
ACFS-9154: Loading 'oracle acfs' driver.
ACFS-9327: Verifying ADVM/ACFS devices.
ACFS-9157: Detecting driver 'oracle oks'.
ACFS-9157: Detecting driver 'oracle advm'.
ACFS-9157: Detecting driver 'oracle acfs'.
ACFS-9322: completed 

Now try to enable a volume.

SQL> alter diskgroup dg1 enable volume dg1_vol1;