You can extend or shrink mounted VxFS file systems using the
fsadm command.Use the
extendfs command to extend the size of an unmounted file system. A file system using the Version 4 disk layout can be up to 2 terabytes - 1 kilobyte in size. A file system using the Version 6 disk layout can be up to 8 exabytes in size. The size to which a Version 6 disk layout file system can be increased depends on the file system block size.
See VxFS Version 6 disk layout.
fdisk(8) manual pages.