Can any one explain the code given below??... Its about the scheduling

<%@ LANGUAGE="VBScript" %>
<% Option Explicit %>
<%
'+---------------------------------------------------+
'| Scheduled Task in Active Server Pages             |
'| Nick Sumner 06.2004                               |
'| http://www.tele-pro.co.uk/                        |
'| dev@nicksumner.com                                |
'+---------------------------------------------------+
'| asp_schedule_task.asp
'| schedule a task in an ASP application
'+---------------------------------------------------+


'call AnyFunction() once every 6 hrs
If (ScheduleTask("MyTaskName", "h", 6)) Then 
  Call AnyFunction()
end If

FUNCTION ScheduleTask(task_name, period, qty)
  Dim RunNow
  Dim last_date
  Dim diff

  'boolean result
  RunNow = False

  'chcek the value of app setting
  last_date = Trim(Application("Sched_" & task_name))

  'is value empty? maybe app just started
  If (last_date = "") Then
    RunNow = True
  Else
    'is value old?
    diff = DateDiff(period, last_date, Now())
    If (diff>=qty) Then RunNow = True
  End if

  'if scheduled to run now, set the app last run time
  If (RunNow) Then Application("Sched_" & task_name) = Now()

  'return result
  ScheduleTask = RunNow 
END FUNCTION 

%>

Code (markup):

 

What explaination do you want? The code checks an application variable and if the difference is greater than the amount noted in the function or if it cannot tell when it was last run it then says to run the function and sets the datetime of the last run as now.

The problem with these types of functions is that it run on the assumption that the application will be running 24/7 however unless you have a constant stream of visitors or have a dedicated server the application will almost certainly be killed to release the memory back to the server thus a proc that is only to run every 24hrs or so will probably run several times in that period.

The second issue is that it requires a page to be called to trigger the function so again will only work if there are a reasonable level of visitors (inc bots) otherwise if you have a script to run ever 5 minutes but you only get page calls on average ever hour then the script will only run on an hourly basis.

Unfortunately IIS/ Windows shared hosting doesnt have the same capabilities as Cron jobs in the LAMP environment.... services are the solution for windows however most shared hosts wont install 3rd party services due to the security risk.