Modifies characteristics of the specified group. The DNS$GroupRevoke
 characteristic specifies a timeout that determines how long a
 positive result from a group membership test operation may be cached
 by the clerk that issued the request.

 SYNOPSIS

      SET GROUP group-name DNS$GroupRevoke

      (expiration-time extension-time)

 Arguments

 group-name

 The full name of the group.

 expiration-time

 A date and time after which a clerk must verify that a principal
 is still a member of a group. The value is specified as yyyy-mm-dd-
 hh:mm:ss.

 extension-time

 A period of time for which to renew the clerk's reliance on cached
 data when checking for group membership. After the specified
 expiration time, a clerk must verify group membership from the
 server. If the test is positive, the clerk adds the extension time
 to obtain a new expiration date. The extension time is specified as
 ddd-hh:mm:ss.

 ACCESS RIGHTS
 You must have write access to the group whose attribute you intend
 to modify.