First you need to identify the volume length maximum in your syntax. Do this
by running the 'vxprint -d' cammand.
Disk group: yourdg

TY NAME ASSOC KSTATE LENGTH PLOFFS STATE TUTIL0
PUTIL0
dm yourdg01 c25t14d3s2 - 86533920 - - -
-
dm yourdg02 c25t14d4s2 - 86533920 - - -
-

Tally up the length of the two disks. So 86533920x2=173067840. So your syntax
would look like this:

vxassist -g yourdg growby vol01 173067840 yourdg01 yourdg02

Good Luck,
JW

"Peter Jones" wrote:
>
>We are trying to mirror a volume but get the following error:
>
>vxvm:vxassist:ERROR:cannot allocate space to mirror 436127744 block volume.
>
>the volume is 208GB and we have 208GB unused disks available. The output
>below is from vxprint -thf and show the volume we are trying to mirror:
>
>v data01 fsgen ENABLED ACTIVE 436127744 SELECT -
>pl data01-01 data01 ENABLED ACTIVE 436129024 CONCAT -

> RW
>sd oracled01-01 data01-01 oracled01 0 348105984 0 c3t4d0
> ENA
>sd oracled02-01 data01-01 oracled02 0 88023040 348105984 c3t4d1
> ENA
>
>I have noticed from this output that the plex size is more than the volume,
>could this be the cause of the problem?
>Regards
>Peter Jones