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Direct Path Reads

發(fā)布時間：2020-08-14 10:25:14 來源：ITPUB博客 閱讀：136 作者：xychong123 欄目：關系型數(shù)據(jù)庫
Oracle Database SQL Tuning Guide---8 Optimizer Access Paths    

Direct Path Reads
In a direct path read, the database reads buffers from disk directly into the PGA, bypassing the SGA entirely.
The following figure shows the difference between scattered and sequential reads, which store buffers in the SGA, and direct path reads.

Situations in which Oracle Database may perform direct path reads include:

  • Execution of a CREATE TABLE AS SELECT statement

  • Execution of an ALTER REBUILD or ALTER MOVE statement

  • Reads from a temporary tablespace

  • Parallel queries

  • Reads from a LOB segment




 
Direct Path Reads

In a direct path read, the database reads buffers from disk directly into the PGA, bypassing the SGA entirely.

The following figure shows the difference between scattered and sequential reads, which store buffers in the SGA, and direct path reads.

Direct Path Reads

In a direct path read, the database reads buffers from disk directly into the PGA, bypassing the SGA entirely.

The following figure shows the difference between scattered and sequential reads, which store buffers in the SGA, and direct path reads.

Direct Path Reads

In a direct path read, the database reads buffers from disk directly into the PGA, bypassing the SGA entirely.

The following figure shows the difference between scattered and sequential reads, which store buffers in the SGA, and direct path reads.

Direct Path Reads

In a direct path read, the database reads buffers from disk directly into the PGA, bypassing the SGA entirely.

The following figure shows the difference between scattered and sequential reads, which store buffers in the SGA, and direct path reads.

Direct Path Reads
In a direct path read, the database reads buffers from disk directly into the PGA, bypassing the SGA entirely.


The following figure shows the difference between scattered and sequential reads, which store buffers in the SGA, and direct path reads.
Direct Path Reads
In a direct path read, the database reads buffers from disk directly into the PGA, bypassing the SGA entirely.


The following figure shows the difference between scattered and sequential reads, which store buffers in the SGA, and direct path reads.
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