Oracle architecture and backup (6) sga-shared_pool

1. What is flock, thedictionarycache, theresultcache, buffersforparallelexecutionmessages, andcontrolstructures. Thisdivincludesthefollowingtopics: LibraryCa

What is shared_pool The shared pool portion of the SGA contains the library cache, the dictionary cache, the result cache, buffers for parallel execution messages, and control structures. this p has des the following topics: Library Ca

1. What is shared_pool?

The shared pool portion of the SGA contains the library cache, the dictionary cache, the result cache, buffers for parallel execution messages, and control structures.

This p includes des the following topics:

Library Cache

The library cache includes des the shared SQL areas, private SQL areas (in the case of a shared server configuration), PL/SQL procedures and packages, and control structures such as locks and library cache handles.

Shared SQL areas are accessible to all users, so the library cache is contained in the shared pool within the SGA.

Dictionary Cache

The data dictionary is a collection of database tables and views containing reference information about the database, its structures, and its users. oracle Database accesses the data dictionary frequently during SQL statement parsing. this access is essential to the continuing operation of Oracle Database.

The data dictionary is accessed so often by Oracle Database that two special locations in memory are designated to hold dictionary data. one area is called the data dictionary cache, also known as the row cache because it holds data as rows instead of buffers (which hold entire blocks of data ). the other area in memory to hold dictionary data is the library cache. all Oracle Database user processes share these two caches for access to data dictionary information.

Result Cache

The result cache is composed of the SQL query result cache and PL/SQL function result cache, which share the same infrastructure.

The DBMS_RESULT_CACHE package provides administration subprograms, which, for example, flush all cached results and turn result-caching on or off systemwide. the dynamic performance views V $ RESULT_CACHE _ * allow the developer and DBA to determine, for example, the cache-hit success for a certain SQL query or PL/SQL function.

Similar to the result cache, the client result cache also caches results, doesn't that the caching is done on the client side.

For storage:

Recently executed SQL statement

Recently used data definition

Consists of three performance-related parts

Library Cache

Data Dictionary Cache

Result Cache

The size is determined by the SHARED_POOL_SIZE parameter.

Example 2

SQL> show parameter shared_pool_size;NAME     TYPE VALUE------------------------------------ ----------- ------------------------------shared_pool_size     big integer 12MSQL> show parameter sga_target;NAME     TYPE VALUE------------------------------------ ----------- ------------------------------sga_target     big integer 160M

Summary

1. Storage: recently executed SQL statements and recently used data definitions;

2. It consists of three performance-related parts: database cache, data dictionary cache, and result cache;

3. You can view the size of the shared pool through the shared_pool_size parameter.

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