Library /sys$common/syshlp/diskquota.hlb MODIFY, /OVERDRAFT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  This qualifer allows the user to specify how many blocks
  (decimal) that a user with a given UIC may use on a given
  volume, OVER AND ABOVE the user's PERMQUOTA limit.  If
  this qualifier is not present or no value is specified, the
  field in the record is not modified.

  EXAMPLE:
   MODIFY [11,17] /OVERDRAFT=200

  This will modify the quota record for UIC [11,17] to set the
  overdraft limit to 200 blocks.