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User needs often cycle over the course of time, based on business needs, such that some users will not find the database to be inaccessible until there is a massive amount of activity in a certain area, and then suddenly there are not enough resources.
Accounts Receivable, at Horatio's Woodscrews, has this problem. As the end of each month comes to a close, they have to close out the previous month's accounts and run massive reports on the status of all opening and closing accounts. This month-end processing sends the database processing needs of the AR department through the roof-but only for a week or so, before it settles back into a more routine usage pattern.
The concept of using different services for different applications in Oracle Database 10g can allow the DBA to set up differing resource limits and thresholds for different applications. Those thresholds can be modified easily using the Resource Manager, allowing different limits to apply to applications at different times. So, at the start of each month, the reporting group can get more resources than at other times during the month, the paycheck group gets month-end, and the orders group gets an annual bump in resource allocation. By combining services and real application clusters, different applications can be allowed access to a differing number of nodes, so that higher priority applications can scale up faster when needed. Services are discussed in more detail in Chapter 6.
At the same time, Human Resources typically finds its peak at the lead-up to the end of the month, as it processes employee hours, salaries, and payments. They will need the most resources, then, at a different time than the AR department.
The reporting of these two groups always affects the Order Entry group, as they have a relatively steady database resource usage pattern over the entire course of the month. However, as the summer approaches, the hardware stores begin to increase the stock of woodscrews, and so orders will steadily increase as the summer approaches, and then steadily decrease as weather cools.
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