Provides you with an in-depth understanding of Oracle SQL scheduler Management

Oracle SQL plan management can improve the performance of SQL statements. The following describes the knowledge of Oracle SQL plan management for your reference.

Oracle SQL Plan Management

How many times have you seen the following situation: a query has the best plan possible, but some things suddenly happen, causing the plan to be discarded. These may be when someone re-analyzes the table, or star_transformation and other parameters that affect the optimizer are changed-there are endless possibilities. Out of despair, you may prohibit any changes to the database, which means that you do not collect database statistics, do not change any parameters, and so on.

However, this is easy to say. What happens when the data mode changes? Take the example shown in the adaptive game tag section as an example. Currently, the CUSTOMERS table is filled with CUSTOMERS from New York, so most of STATE_CODE is "NY ". Therefore, when you execute a query that contains the following predicates:

Where state_code = 'ct'

The system performs a full table scan instead of an index scan. When the predicate is:
Where state_code = 'ct'

The system uses indexes because only several rows of results are returned. However, if the pattern changes-assuming that a large number of customers suddenly emerge from Connecticut (state_code = 'ct '), the percentage of Results containing CT increases to 70%. What will happen at this time? In this case, full table scan should be used for CT queries. However, because you have disabled collection of optimizer statistics, the optimizer does not understand pattern changes and will continue to provide inefficient index scan paths. What can you do?

If Oracle uses an optimal plan, but the plan is re-evaluated when underlying factors such as statistical data collection or database parameters change, the database will be used only when the new plan is more effective, what are the results? This solution is ideal, isn't it? It has become possible in Oracle Database 11 GB.

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