Processing Stored Data

Now that there is a plan for accessing the files, they can be processed. There are several methods of processing data files in a computer system. Thw two main methods are batch processing ( processing data in groups at a more convenient later time) and transaction processing ( processing data immediately, as it is recieved).

Batch Processing

Batch processing is technique in which transactions are collected into groups, or batches, to be processed at a time when the computer may have few online users and thus be more accessible, usually during the night Unlike transaction processing, which we will examine momentarily, batch processing includes no direct user interaction. Let us suppose that we are going to update the health club addres-label file. The master file, a semi permanent set of record, is, in this case, he list of all members of the health club and their addresses. The transaction file contains all changes to be made to the master file: addition (transaction to create new master record for new members), deletions (transaction with instruction to delete master record of members who have resigned from the health club), and revisions (transaction to change items such as street addresses or phone numbers, in fields in the master records). Periodecally, perhaps monthly or weekly, the master file is updated with the changes called for in the transaction file. the result is a new, up-to date master file.

In batch processing, before a transaction, before a transaction file is matched against a master file, teh transaction file must be sorted ( usually by computer) so that all the transactions are in sequential order according to a key field. In updating the health club address-label file, the key is the member number assigned by the health club. The record on the masterfile are already in order by key. Once the changes on the transaction file are sorted by key, the two file can be matched and the master file updated.

During processing, the computer matches the keys from the master and transaction files, carrying out the appropriate action to add, revise, or delete. At the and of processing, a newly updated master file is created; in addition, an error report is usually printed. The error report shows actions such as an attempt to delete a nonexistent record or an attempt to add a record that already exists.

Transaction Processing

Transaction processing is a technique of processing transactions-a bank withdrawal, an address change, a credit charge-in random order, that is, in any order they occur. Transaction processing is real-time processing. Real-time processing means that a transaction is processed fast enough for the result to come back and be acted upon righ away. for example, a teller at a bank can find out immediately what your bank balance is. For processing to be real-time, it must also be online-that is, the terminals must be connected directly to the computer. Transaction processing system use disk storage because the disk drive can move directly to the desired record.

Advantages of transaction processing are immediate updating of the stored data (and thus immediate customer service), and immediate updating of the stored data. A salesclerk, for example, could acces the computer via a terminal to verify the customer's credit and also record the sale via the computer. Later, by the way, those updated records can be batch processed to bill all customers.

Batch transaction processing

Batch and Transaction Processing: The Best of Both Worlds

Nomerous computer systems combine the best features of both method of processing. A bank for instance, may use transaction processing to check your balance and individually record your cash withdrawal transaction during the day at the teller window. However, the deposit that you leave in an envelope in an " instant" deposit drop may be recorded during the night by means of batch processing. Most store system also combine both methods: a point-of-sale terminal finds the individual item price as a sale is made. But the same process captures inventory data, wich may be batched and totaled to produce inventory reports.

Police licese-plate check for stolen cars work the same way. As cars are sold throughout the state, the license numbers,owners' names, and so on, are updated in the motor vehicle department's master file, usually via batch processing on a nightly basis. But when police officers see a car they suspect may be stolen, they can radio headquarters, where can operator with a terminal uses trasaction processing to check the master file immediately to see if the car was reported missing.

What is the future of storage? Perhaps holographic storage, which would provide gigabytes of capacity and be much faster than even the fastest hard driver. Whatever the technology, it seems likely that we will be seeing greater storage capabilities in the future to hold the huge data file for law, medicine, science, education, business, and of course, the goverment.

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