Transcription of Best Practices for Gathering Optimizer Statistics with ...
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Best Practices for Gathering Optimizer Statistics with ...
Best Practices for Gathering Optimizer Statistics with oracle database 12c Release 2 O R A C L E W H I T E P A P E R | J U N E 2 0 1 7 BEST Practices FOR Gathering Optimizer Statistics WITH oracle database 12C RELEASE 2 Table of Contents Introduction 1 How to Gather Statistics 1 When to Gather Statistics 7 Assuring the Quality of Optimizer Statistics 11 Gathering Statistics More Quickly 13 When Not to Gather Statistics 16 Gathering Other Types of Statistics 18 Conclusion 20 References 21 1 Introduction The oracle Optimizer examines all of the possible plans for a SQL statement and picks the one with the lowest cost, where cost represents the estimated resource usage for a given plan.
The Oracle database collects statistics for database objects that are missing statistics or have “stale” (out of date) statistics. This is done by an automatic task that executes during a predefined maintenance window. Oracle internally prioritizes the database objects that require statistics, so that those objects, which most need updated
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