You can extend or shrink mounted VxFS file systems using the fsadm command. The size to which a file system can be increased depends on the file system disk layout version. A file system using the Version 7 or later disk layout can be up to eight exabytes in size. The size to which a Version 7 or later disk layout file system can be increased depends on the file system block size.

See the format(1M) and fsadm_vxfs(1M) manual pages.