You may face any number of these and other situations each day. You should have a backup or contingency plan in the event you lose a piece of hardware. For example, if the fastest printer is down, will the user be satisfied with one printed copy now and the  remaining  copies  printed  tomorrow?  Or  is  there another AIS facility in your immediate area that will let you use its printer? It will be your job to prepare the most realistic schedule you can, and then be ready to adjust it. What tools will you have to help you prepare the schedules? What information will you need? What methods can you use? In the following section, we talk about the types of information you will need to prepare a schedule. Then we explore a few of the scheduling methods you might use. INFORMATION NEEDS Regardless of the scheduling method used, you will need to know specific types of information. Some information is  job-related;  that is, information about the resources, media, and time needed for a particular job. Some information is AIS facility-related; for example, workload,  anticipated  resource  changes,  number  of operators  available,  the  system  capabilities  and capacities, and so on. You will need to consider both. Let’s look at the job-related and AIS facility-related areas in a little more depth. One of the most apparent pieces of job-related information is that every job has resource requirements. These requirements vary considerably from one job to the next. One job may require 125K of memory with no other peripheral devices except a printer for output. Another job may require four tape drives, two disk drives, a printer, and only 40K of memory. But a job’s resources cannot be looked at in these terms alone. Can you recall the terms PREcomputer and POSTcomputer processing?  All  AIS  facility  resources  must  be considered. You must consider data entry functions, job setup   functions,   and   output   control   functions. Overloading  data  entry  can  delay  jobs,  causing  them  to be  assembled  for  computer  processing  later  than scheduled. Suppose I/O control is overloaded. What difference would it make if jobs were processed and completed as scheduled? They would only be delayed because  work  is  backed  up  or  personnel  are  not available. Overutilization of resources affects service. Underutilization of resources is expensive and wasteful. The balance will be up to you and the efficiency of your schedule. Another  piece  of  job-related  information  to consider is processing time. To set aside a sufficient amount of time for processing, you must know how long a job will reside in memory. Processing time is normally  estimated  for  a  multiprogramming environment since most computers today process programs/data in this fashion, and job mix affects the overall processing time for a job. Let’s assume you have a static workload with no jobs being added to or deleted from the schedule. Even under these conditions, you can expect job processing to deviate from the schedule. Why? you might ask. The reasons for this are the uncertainty about job processing time and disrupted processing. Take, for example, a job that normally has a processing time of 45 minutes. Today, because of a large increase in input, the job processing  time  is  1  hour,  thus  delaying  all  the following jobs by 15 minutes. This is unavoidable and must  be  expected.  The  same  is  true  of  disrupted processing, whether it is hardware failure or software problems. One way to avoid these delays is to include a specified amount of buffer time in your schedule. You might add a safety factor of 10 percent to the expected processing  time.  In  our  previous  example  where processing time increased from 45 minutes to 1 hour, a buffer time of 10 percent would only give you an additional 4.5 minutes of processing time. This would still have been inadequate. However, since all the following  jobs  also  have  buffer  time  built  into  their scheduled processing time, the job overrun should not be that critical for meeting the overall schedule of a shift. Another  piece  of  job-related  information  to consider  applies  to  multiprogramming  environments. The challenge here is to combine as many jobs as possible so that each resource is used to its maximum. In a nonmultiprogramming environment, you have no problem in scheduling jobs because you can process only  one  job  at  a  time.  However,  resources  are underutilized, and that’s a fact you must live with. This is a direct result of having all resources dedicated to one computer, even when they are not needed. On the other hand,  multiprogramming  allows  you  to  execute  several jobs at the same time using as many resources as possible. The difficulty of manually preparing such a schedule for a system that runs in a multiprogramming environment is in trying to obtain a job mix that makes the best use of most resources without bogging down the entire computer system. Figure 1-5 gives you some idea of how main storage and peripherals can be fully utilized as a result of the proper job mix. It shows where the jobs are in memory, and what tapes and disk drives are used by each job. It also shows information about printing and printers. It 1-14