#vxdg import testdg
VxVM vxdg ERROR V-5-1-10978 Diskgroup testdg: import failed: System error in configuration copy.

#vxdg init datadg datadg01=hds9500-alua0_0026
VxVM vxdg ERROR V-5-1-585 Diskgroup datadg: cannot create: System error in configuration copy.

This error will occur if the /var/vxm/tmpdb is a file instead of a directory.
#ls -l /var/vxvm/
total 2
-rw-r--r--   1 root    root           0 Jul 28 11:17 tempdb

Removing the file will solve the issue. It will be created upon importing the disk group or upon creating a new one.
#rm /var/vxvm/tempdb

#vxdg import testdg

#vxdg list
NAME        STATE           ID
testdg      enabled,cds          1233776287.56.walv215-a1g

#ls-l /var/vxvm/
total 4
drwxr-xr-x   2 root    root         512 Jul 28 12:14 tempdb