How to extend the size of an LVM volume RHEL5?

[Dave Martini]

Trying to extend the size of a mirrored lvm volume but get this error

# lvextend -L+3G /dev/appsdata/apps1
  Extending 2 mirror images.
  Mirrors cannot be resized while active yet.

I tried unmounting the file system but get the same error.
Anyone know how to do this?
Thanks.
Dave Martini

# lvdisplay
  --- Logical volume ---
  LV Name                /dev/appsdata/apps1
  VG Name                appsdata
  LV UUID                ViPcM1-x20X-fzBG-Og7c-pzvP-ddJa-DLB0lL
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                21.49 GB
  Current LE             5502
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:3