To make grasping the overall concept of work management easier, try comparing your system with a business.
A simple system can be compared to a small business, and a complex system can be compared to a shopping mall. Assume there is a small store in the business of building hand-crafted wood furniture. Work enters, such as orders for small tables, chairs, and bookshelves. Work is processed, the carpenter calls the customers to confirm the order, and they are consulted on design points including style, size, and color. The carpenter designs each piece of furniture, gathers the necessary materials, and then builds the furniture. After the furniture is completed, it is delivered: work leaves.
Since a complex system is a combination of many simple systems, a comparable example of a complex system is a shopping mall, many small and large businesses in one area. Maybe the carpenter has a business in the Northwest corner of the mall and a baker has a business along the East strip. The baker and the carpenter have different input and different output, that is, their orders and their products are very different. In addition, the time it takes each business to process their work is quite different, and their users know and understand that.
A complex system (shopping mall) is a compilation of many simple systems (stores). These simple systems are called subsystems.
Any piece of work within the business is considered a job. An example of a piece of work might be a customer letter, a telephone call, an order, or nightly cleanup. The same can be said about the IBM® iSeries™ system. On the system, each job has a unique name.
A job description describes how to handle the work coming into the subsystem. Job descriptions contain pieces of information such as user IDs, job queues, and routing data. Information in the job description might compare to descriptions of jobs in a small business.
What does the business look like? Every store has blueprints or store plans. These plans are really just descriptions, in varying detail, of the physical makeup of the business. Maybe the business has a store with: 2 floors, 5 doors, 3 mailboxes, and 2 telephones. On the iSeries system, a subsystem description contains all the information about the subsystem.
Where does the work come from? For the carpenter, the work comes from customer calls, from references, and from people that stop in. On the iSeries system, the work can come from many places. Examples include job queues, workstations, communications, autostart jobs, and prestart jobs.
Where do they find the space? Within the mall, each business (subsystem) has a certain amount of floor space. On the iSeries system, memory pools allow you to control the main storage (or floor space) each subsystem (business) gets to do its work. The more floor space a store (subsystem) has, the more customers, or jobs, can fit in the store.
How does the work come in? Customers that cannot find the store they need may find an information booth to help send them in the right direction. The same is true on the iSeries system. Routing entries are similar to store directories or an information booth. After the routing entry is found, it guides the job to its correct place. The routing entry needs to be found first, however. That is done through routing data. Routing data is what the job uses to find the right routing entry.
How is the work treated? A carpenter needs to place a priority on each job. The chair due at the end of the week should be done before the bookshelf due at the end of the month. On the iSeries system, classes provide information about how the job is handled while in the subsystem. This information includes priority while running, maximum storage, maximum CPU time, and time slice. Each of these attributes contribute to how and when a job is processed.
Just as there are rules that affect all the stores in the mall, there are rules that affect all the subsystems on the iSeries system. An example of these rules is a system value. System values are pieces of information that apply to the whole system. System values include information such as, date and time, configuration information, signon information, system security and, storage handling.
Customers in a mall each have information specific to them. On the iSeries system, the user profile holds information specific to a particular user. Similar to a customer’s credit card, a user profile gives that user specific authorities and assigns the user attributes for that user's jobs. These job attributes provide information that includes, but is not limited to, the job description, the output queue or printer device, the message queue, the accounting code, and the scheduling priority.