Test the Consistent gets function in Oracle

1. Consistentgets description

When we use autotrace to view execution plans and statistics, the following information is displayed:

0 recursive cballs: recursive call. General cause: dictionary cache miss; dynamic storage expansion; PL/SQL statement

0 db block gets: BuferReadBlockQuantity, usedInsert, update, delete, selectfor update

174530 consistent gets:Here is the number of consistent reads (oneBlockMay be read multiple times ),BuferRead inSelect forupdate)BlockQuantity.

-- Db blocksgets + consistent gets = logical read

0 physical reads: number of blocks read from the disk

0 redo size: bytes, data volume written to redo logs

3546854 bytes sent via SQL * Net to client

60244 bytes encoded ed via SQL * Net from client

5433 SQL * Net roundtrips to/from client

0 sorts (memory): memory sorting times

0 sorts (disk): The number of disk sorting times, which is related to sort_area_size.

81467 rows processed

 

 

Official Website for consistent getsExplanation:

Consistent gets: Number of times a consistent read wasrequested for a block.

 

Generally, every block involved in SQL query is Consistent Read, but some CR (Consistent Read) needs to be constructed using undo. Most CR (Consistent Read) undo block reading is not involved.

In addition, each Read of this block is a CR (each block may have multiple data rows), that is, if a block is Read 10 times, the system records 10 Consistent reads.

 

To put it simply:

Consistentgets: block read by select without for update.

Dbblock gets: blocks read through update/delete/selectfor update.

 

Db block gets + consistent gets = entire logical read.

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