To eliminate the need to use the "-g" option with commands, a default disk group can be created.
e.g.
# vxassist make vol01 10m
VxVM vxassist ERROR V-5-1-5455 Operation requires a disk group

To check what the default disk group is,  enter the following:
# vxdg defaultdg
nodg

The above output indicates that no disk group has been defined.

To define a disk group,  enter the following:
# vxdctl defaultdg
e.g.
# vxdctl defaultdg EMC

Check the default disk group:
# vxdg defaultdg
EMC

This can also be verified with the following:
# vxdctl list
Volboot file
version:3/1
seqno:  0.5
cluster protocol version: 70
hostid:  punjab
defaultdg:  EMC