create procedure limit_user_sessions_host
as
declare @cnt int,
@limit int,
@loginname varchar(32),
@limit_host int,
@hostname varchar(32),
@cnt_host int

select @limit = 16 -- max nr. of concurrent logins
select @limit_host = 4 -- max nr. of concurrent logins per host


/* determine current #sessions */
select @cnt = count(*)
from master.dbo.sysprocesses
where suid = suser_id()

select @cnt_host = count(*)
from master.dbo.sysprocesses
where suid = suser_id() and
      isnull(hostname, "не определён") = isnull(host_name(), "не определён")  

/*CHAPTER 17 Managing User Permissions
System Administration Guide: Volume 1 551*/
/* check the limit */
if @cnt > @limit or @cnt_host > @limit_host
begin
select @loginname = suser_name()
select @hostname = isnull(host_name(), "не определён")
print "Aborting login [%1!]: exceeds session
limit [%2!] or exceeds session per host [%3!] limit [%4!]",
@loginname, @limit, @hostname, @limit_host
/* abort this session */
select syb_quit()
end
go
grant exec on limit_user_sessions_host to public 

sp_modifylogin <login>, 'login script', limit_user_sessions_host