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The problem with attempting to allocate the correct resources to the correct applications at the correct time of month or year is that often it is nearly impossible to get trended data on usage over time.
The DBA at Horatio's Woodscrews is faced with this dilemma. The different application groups have been complaining about the performance of their reports at different times, but the DBA has not been able to get accurate data on which problem reports or application batch processes are truly in need of more resources. He's been reading up on his performance tuning techniques, but the month is coming to an end again, and he can already hear his pager beginning to beep.
With Oracle Database 10g, the Automatic Workload Repository (AWR) collects performance information every hour, and stores it in the Workload Repository for a week so that the HA DBA can go back and review historical information and past performance issues. In addition, baselines can be maintained indefinitely, so that the HA DBA can compare problem periods to points in the past when things were running smoothly. The Automatic Database Diagnostic Monitor, or ADDM, runs at the end of every AWR report period and proactively reports on any discovered problems, as well as recommending solutions or running additional tuning advisors. We discuss this in more detail in Chapter 3.
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