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 two terabytes in size. A file system using the Version 5 disk layout can be up to 32 terabytes in size. A file system using the Version 6 disk layout can be up to 256 terabytes in size. The size to which a Version 5 or Version 6 disk layout file system can be increased depends on the file system block size.
See VxFS Version 5 disk layout and VxFS Version 6 disk layout.
sadm_vxfs(1M) manual pages.