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Parallel Processing

Statement-level PARALLEL Hint

From version 11.2 onward, the PARALLEL hint supports two syntaxes: object-level and statement-level. The object-level syntax, which is the only one available up to version 11.1, overrides the DOP associated to a tables. The statement-level syntax can not only override the PARALLEL_DEGREE_POLICY initialization parameter at the SQL statement level, but also force the utilization of parallel processing.

The statement-level PARALLEL hint supports the following values:

Parallel Full Table Scans Do Not Always Perform Direct Reads

Even though in general parallel full table scans performs direct reads, some exceptions exist. The aim of this post is to show such an exception.
For test purposes I build in my own schema a copy of the SH.SALES table (the one distributed by Oracle with the demo schemas…). On that table I build an [...]

Parallel Processing With Standard Edition

As clearly stated in the Licensing Information guide, all features related to parallel processing (parallel backup and recovery, parallel query/DML, parallel statistics gathering, parallel index build/scans, parallel Data Pump export/import, in-memory parallel execution, parallel statement queuing and parallel spatial index builds) are only available with the Enterprise Edition. However, as of Oracle Database 11g Release [...]

Exadata Storage Server and the Query Optimizer – Part 3

In the first and second post of this series I shared with you some basics about smart scan and gave some details about projection and restriction. The aim of this post is to cover the third basic technique: join filtering.
Join filtering is not something specific to the Exadata Storage Server. In fact, it is an [...]

Does the Query Optimizer Cost PX Distribution Methods?

The short answer to this question is “yes”, it does. Unfortunately, the distribution costs are not externalized through the execution plans and, as a result, this limitation (yes, it is really a limitation in the current implementation, not a bug) confuses everyone that carefully look at the information provided in an execution plan of a [...]