MANUAL VERSUS AUTOMATED SCHEDULING

One of the key decisions to be made when developing a scheduling system is whether to use a manual or automated system. Much more must be consid-ered than the cost of a package to automate the scheduling function versus the current investment in talent in the data center. This section deals with the issues that should be considered in making this decision and includes a com-parison of the two approaches. This is a very critical decision because the investment for the system will be significant and a wrong decision can be costly. A manual system may seem like the safest choice since it can be converted into an automated system; however, this is not always the case. The standards developed for a manual system may have to be changed, and people will have to be retrained for such a conversion. These changes can result in significant costs.

Characteristics of a Manual System

Manual scheduling systems can and do work well. Many data centers have used manual methods successfully for years. There are advantages and disad-vantages to this approach, each of which should be weighed as it relates to the DCOM's organization. A manual system can bring the following advantages:

• Simple block scheduling techniques-Manual systems are character-ized by the use of simple block scheduling methods. The advantage of this methodology is that it is easily understood by management, users, and data center personnel, thereby enabling easy implementation of the schedule for all concerned.

• Machine-independent-Manual schedules are usually developed at a desk. There is little, if any, need for the use of the computer to produce the schedule.

• Less up-front cost-Manual systems usually have a low start-up cost because primary materials for the system are forms and scheduling boards. These items are inexpensive compared with the price of an automated scheduling package.

• More personal-Because the manual system uses simple scheduling techniques, it is more easily understood by the personnel it affects. A personal touch, which is lost in the technical details of an automated system, is possible with a manual system. In some data centers, the personal handling of problems between users and the scheduling de-partment helps to maintain a high level of DP credibility.

• Short development time-Because manual systems require no program-ming and use a forms approach, they can usually be developed in a relatively short period of time. This can be helpful if current scheduling problems are severe and a quick solution is required.

• Allows evolution to an automated system-If a manual system is

prop-DEVELOPING A SCHEDULING SYSTEM 57

erly designed and installed, the standards employed should allow the system to be automated if required. This consideration is important in a small data center that is growing rapidly. On the other hand, it may be very difficult to change from an automated system to a manual system without embarrassment to the DCOM and considerable inconvenience to the organization.

• Small-organization use-A manual system can be the best approach for the small data center or the center with a low work load level. Many of the advantages of the automated approach are negated if the data center has excess capacity; in such cases a manual approach may more than suffice.

The disadvantages of a manual scheduling system should also be consid-ered:

• People dependent-A manual scheduling system requires personnel to develop and maintain the operating schedules. Before choosing a man-ual system the DCOM should seriously consider the capability of his staff in order to ensure that the talent and time needed to make the system effective are available.

• Problems projecting the impact of changes-Manual systems cannot instantly reschedule everything in response to an operating or user crisis. Because of this, it is difficult to predict the future impact of priority changes, especially if many functions are scheduled. This is a fundamental weakness in manual systems, although a good scheduler who really knows the shop can do a fairly good job making such changes. In a large center, however, it is almost impossible to perfonn this task manually. The DCOM should consider whether the frequency of rescheduling in his data center warrants the installation of an auto-mated system.

• Fewer considerations can be handled-Because of limitations, manual systems typically deal with fewer scheduling considerations than do automated systems. It is usually difficult to consider factors beyond date/time due and predecessor-successor relationships. Some of these factors can be important, particularly if the schedule is tight because they can improve throughput by making scheduling more effective.

These factors include CPU to I/O mix in the system, increasing run-time experience with a job during a processing cycle, and so on.

• Less accuracy and more susceptibility to judgment errors-Because manual systems typically use less data to develop the schedule and because of unavoidable human errors, manual systems are less accurate than automated systems. This may not be crucial if the center has effective backup/restore procedures. If a data center is overloaded and a significant percentage of the work is reruns, a manual system may not reduce reruns as much as desired. In addition, since scheduling person-nel usually deal with production jobs, they often have difficulty making proper decisions about priorities for test work.

• Difficulty plotting history or predicting trends-Most manual systems are designed to schedule the current activities of the data center rather

58 DATA CENTER OPERA nONS MANAGEMENT

than to track past activities. The absence of this capability makes it difficult to use the system to analyze historical developments or to project trends. This may be a serious shortcoming in a rapidly expand-ing environment where good plannexpand-ing data is a must.

• Tendency to overkill-Some data centers always run the most critical job in the shop first, regardless of when the job is due; their only scheduling criteria are the availability of the job and its criticality. This is a nonproductive method of scheduling because it pays little attention to noncritical jobs and programmer testing. Often programmers are left idle while the data center runs jobs that could be scheduled at night.

This is a very wasteful practice, and manual systems can do little to restrict it.

Characteristics of Automated Systems

Automated scheduling systems vary widely in capability and cost. This includes systems developed in-house. Most automated systems offer the fol-lowing advantages:

• Standards enforcement-For an organization that has standards or wants to implement them, one of the advantages of an automated system is that it can enforce such standards as job numbers, job names, program numbers, account numbers, and so on.

• Trend analysis-An effective automated system provides the ability to examine data center trends. Trends can be predicted for a single job, an application, or the whole system and can be helpful for projecting future work loads on a given system.

• Disaster and capacity planning-Many automated systems allow the data center to identify disaster backup requirements by automatically identifying me updates. An automated system can also be useful as a modeling tool in capacity planning. By running a proposed configura-tion on the scheduling system, planners can predict the benefits of adding, upgrading, or reducing equipment.

• Priorities and unforeseen work load handling-Although it may require a scheduling run through the computer, a good automated system can show the impact of changing priorities or adding new work. In such situations the DCOM may only be able to get the "hot job" out, but at least he can notify other users of delays before they actually occur.

This is helpful if delays are significant. An automated system also works to minimize the impact of the change by attempting to catch up as quickly as possible. It is conceivable that a priority change could necessitate a complete rescheduling, and an automated system can accomplish this much faster than a manual system.

• Throughput optimization within scheduling constraints-A good sched-uling system will optimize throughput if the input is available early enough to allow flexibility.

• Self-educating-A good system can "educate" itself as it gains experi-ence with a particular job, enabling it to schedule the work into tighter

DEVELOPING A SCHEDULING SYSTEM 59 time frames and to be more precise about the requirements for running the job.

• Better production/nonproduction work load mix-automated systems schedule based on time due out and resources required. If production work is entered into the system early enough, the scheduler should attempt to optimize throughput by mixing work that runs well together.

It is also possible to reserve periods of time for programmer testing by having the scheduler give priority to testing unless a production com-mitment is due.

• High accuracy-Under normal circumstances, automated systems will never forget to schedule a job. Automated systems are accurate even in long-range scheduling. This is useful when planning new applications or jobs because it enables planners to determine the impact of the new addition over a longer period of time.

• Adaptable to growth-Because of their ability to track the history of jobs and examine trends, automated systems are very adaptable in situations where the data center is growing quickly. In such an environ-ment the scheduling system may be the only reliable source of planning data.

• People independent-Automated systems allow the scheduling group to code scheduling logic without programming. Once coded, these sys-tems are not dependent on personnel. A good system should be well documented and easy to learn, further reducing dependence on particu-lar individuals in the organization.

• High start-up costs-Whether developed internally or purchased, most automated systems will have a high start-up cost. In an organization with limited resources, this can be a serious shortcoming. The DCOM must ensure that sufficient resources exist to implement the system. If there are any doubts, the DCOM may want to consider lower-cost options or a manual system.

• Long development time-Because of the sophistication of the data used for scheduling and the length of time needed to develop or tailor programs, an automated scheduling system usually has a long develop-ment time. If the DCOM wants immediate benefits, he should consider another approach, at least on an interim basis.

• Standardization-If the DCOM's organization has no standards (partic-ularly for job numbering), he will have difficulty implementing an automated system. Standards have benefits in themselves and should be considered by all organizations; however, if they do not exist and will not be developed, the DCOM should consider another scheduling approach.