oracle9 i performance tuning

Oracle9Oracle9ii Performance TuningPerformance Tuning

Chapter 4Chapter 4

Tuning the Shared Pool MemoryTuning the Shared Pool Memory

Chapter 4: Tuning the Shared Pool Memory 2

Chapter ObjectivesChapter Objectives• Understand the role of the Shared Pool Memory• Learn Shared Pool Advice terms• Learn terms for the internal structures of the Shared Pool

Memory• Learn the role of the library cache and data dictionary cache• Configure the Shared Pool Memory• Use the Shared Pool Size Advice feature


Chapter Objectives Chapter Objectives (continued)(continued)

• Diagnose the Shared Pool Memory configuration• Look inside the Shared Pool Memory using performance

dynamic views• Flush the Shared Pool Memory• Pin objects in Shared Pool Memory• Understand and configure the Large Pool• Understand and configure Java Pool


Oracle ArchitectureOracle Architecture


Data ClassificationData Classification• User and system data is stored and retrieved in a data User and system data is stored and retrieved in a data

file and cached in the buffer cachefile and cached in the buffer cache• Transaction data consists of all the DMLs and DDLs Transaction data consists of all the DMLs and DDLs

issued against the databaseissued against the database• Data is cached in the log buffer and ultimately stored in the Data is cached in the log buffer and ultimately stored in the

redo log filesredo log files• SQL statements and PL/SQL blocks data consists of the SQL statements and PL/SQL blocks data consists of the

SQL and PL/SQL code issued against the databaseSQL and PL/SQL code issued against the database• It is cached in shared pool memoryIt is cached in shared pool memory


Data Classification Data Classification (continued)(continued)

• Database objects definition data is retrieved from Database objects definition data is retrieved from system data files and cached in the shared poolsystem data files and cached in the shared pool• Database objects definition data contains metadata about the Database objects definition data contains metadata about the

database object structures and privilegesdatabase object structures and privileges• Java code data consists of Java-related code, which is Java code data consists of Java-related code, which is

loaded and executed by different sessionsloaded and executed by different sessions• It is cached in the Java poolIt is cached in the Java pool

• Buffered data can be from any of the above Buffered data can be from any of the above classifications, but is buffered in the large poolclassifications, but is buffered in the large pool


Data Classification Data Classification (continued)(continued)


Processing SQL StatementsProcessing SQL Statements


Processing PL/SQL BlocksProcessing PL/SQL Blocks


SQL Statement Processing TasksSQL Statement Processing Tasks


Shared Pool Memory Performance Shared Pool Memory Performance TermsTerms• Hard parse: When a statement is submitted and is not found in Hard parse: When a statement is submitted and is not found in

memory, a hard parse is performedmemory, a hard parse is performed• Hard parses use considerably more resources than soft parsesHard parses use considerably more resources than soft parses

• Soft parse: Occurs when a SQL statement is found in memory and can Soft parse: Occurs when a SQL statement is found in memory and can be reusedbe reused

• Execute call: A call to execute a SQL statement. Execute call: A call to execute a SQL statement. • If the statement is already parsed, a soft parse occurs, but if the statement If the statement is already parsed, a soft parse occurs, but if the statement

has been aged out from memory, a hard parse occurshas been aged out from memory, a hard parse occurs• Parse call: A call to parse a SQL statement because it was not found in Parse call: A call to parse a SQL statement because it was not found in

memorymemory• Bind variable:Bind variable: The process of passing a variable from the calling The process of passing a variable from the calling

environment such as SQL*Plus, Oracle Forms, Oracle Reports, and environment such as SQL*Plus, Oracle Forms, Oracle Reports, and other Oracle development toolsother Oracle development tools


Shared Pool Memory Performance Shared Pool Memory Performance TermsTerms• Hash function: An algorithm used to convert the submitted SQL Hash function: An algorithm used to convert the submitted SQL

statement to a hash value, which can be compared to hash values stored statement to a hash value, which can be compared to hash values stored in memory to determine if the statement is already in memoryin memory to determine if the statement is already in memory

• Reloads: The number of times a cached SQL statement was reloaded or Reloads: The number of times a cached SQL statement was reloaded or reparsed because the statement was aged outreparsed because the statement was aged out

• Invalidations: The number of times a cached SQL statement became Invalidations: The number of times a cached SQL statement became invalid and could not be shared because there was a modification to the invalid and could not be shared because there was a modification to the database objects used by the statementdatabase objects used by the statement

• Library cache hit: Synonymous with soft parseLibrary cache hit: Synonymous with soft parse• Library cache miss:Library cache miss: Synonymous with hard parseSynonymous with hard parse


Shared Pool Memory Internal Shared Pool Memory Internal StructureStructure• Library cache: A major memory space of the shared pool memory used to Library cache: A major memory space of the shared pool memory used to

cache SQL statements, PL/SQL blocks, and other object code used by the cache SQL statements, PL/SQL blocks, and other object code used by the applicationapplication

• Data dictionary cache: A major memory space of the shared pool memory Data dictionary cache: A major memory space of the shared pool memory used to store database object definitions temporarilyused to store database object definitions temporarily

• Character set structure: A space in memory used to store the character set Character set structure: A space in memory used to store the character set used by the Oracle instanceused by the Oracle instance

• Locks structures: Data structures used to synchronize and coordinate access to Locks structures: Data structures used to synchronize and coordinate access to database objectsdatabase objects

• Latches structures: Data structures used as mechanisms to protect memory Latches structures: Data structures used as mechanisms to protect memory while it is in usewhile it is in use

• Enqueues structures:Enqueues structures: Data structures used for serial access to the database in a Data structures used for serial access to the database in a Real Application Cluster (RAC) or in a standalone instanceReal Application Cluster (RAC) or in a standalone instance


Shared Pool Memory Internal Shared Pool Memory Internal StructureStructure


V$LIBRARY_CACHE_MEMORYV$LIBRARY_CACHE_MEMORY


V$LIBRARY_CACHE_MEMORY V$LIBRARY_CACHE_MEMORY (continued)(continued)


Shared Pool Size AdviceShared Pool Size Advice• Provides advisory statistics for the shared pool memoryProvides advisory statistics for the shared pool memory

• Use the dynamic performance view V$SHARED_POOL_ADVICEUse the dynamic performance view V$SHARED_POOL_ADVICE


V$LIBRARYCACHEV$LIBRARYCACHE


Library Cache Hit RatioLibrary Cache Hit Ratio


Library Cache Diagnosis Library Cache Diagnosis


Library Cache Diagnosis Library Cache Diagnosis (continued)(continued)

• GETHITRATIO value:GETHITRATIO value:

• PINHITRATIO value:PINHITRATIO value:

• RELOADS Ratio:RELOADS Ratio:


Library Cache Diagnosis Library Cache Diagnosis (continued)(continued)

• INVALIDATIONS Ratio:INVALIDATIONS Ratio:

• RELOADS to PINS Ratio:RELOADS to PINS Ratio:


Data Dictionary DiagnosisData Dictionary Diagnosis


Data Dictionary Diagnosis Data Dictionary Diagnosis (continued)(continued)


Shared Pool Memory Usage Shared Pool Memory Usage


Shared Pool Memory Usage Shared Pool Memory Usage (continued)(continued)


Shared Pool Free MemoryShared Pool Free Memory


Shared Pool Free Memory Shared Pool Free Memory (continued)(continued)


Using Oracle Enterprise ManagerUsing Oracle Enterprise Manager


TopSQLTopSQL


Looking Inside Shared Pool MemoryLooking Inside Shared Pool MemoryUsing V$DB_OBJECT_CACHEUsing V$DB_OBJECT_CACHE


Looking Inside Shared Pool MemoryLooking Inside Shared Pool MemoryUsing V$DB_OBJECT_CACHE Using V$DB_OBJECT_CACHE (continued)(continued)


Looking Inside Shared Pool MemoryLooking Inside Shared Pool Memory• V$OBJECT_USAGEV$OBJECT_USAGE• V$SQLV$SQL• V$SQLAREAV$SQLAREA• V$SQLTEXTV$SQLTEXT• V$SQLTEXT_WITH_NEWLINESV$SQLTEXT_WITH_NEWLINES


Managing Shared Pool MemoryManaging Shared Pool MemoryFlushing the Shared Pool MemoryFlushing the Shared Pool Memory

Pinning ObjectsPinning Objects


CURSOR_SHARING ParameterCURSOR_SHARING Parameter


CURSOR_SPACE_FOR_TIME CURSOR_SPACE_FOR_TIME ParameterParameter


Large Pool MemoryLarge Pool Memory• The large pool memory is an optional structure of the

SGA• It is configured by the LARGE_POOL_SIZE parameter• It is used as a temporary placeholder for special It is used as a temporary placeholder for special

programs and functionality as follows:programs and functionality as follows:• Recovery Manager (RMAN)Recovery Manager (RMAN)• Shared server, formerly known as Multithreaded server Shared server, formerly known as Multithreaded server

(MTS)(MTS)• PARALLEL_AUTOMATIC_TUNING optionPARALLEL_AUTOMATIC_TUNING option• Parallel queryParallel query


Java PoolJava Pool• The Java pool is an optional structure of the SGA

• It is configured by the JAVA_POOL_SIZE parameter

• It is used to cache executed Java programs, Java classes, and other Java-related objects


SummarySummary• The shared pool memory is an important structure of the SGA

used to cache SQL statements, PL/SQL blocks, and other memory objects to reduce CPU consumption and I/O trips to data files

• SQL statements are processed in three steps: 1. The statements are parsed for syntax validity, user privileges are

verified, and a plan for retrieving data is created2. The plan created in the first step is executed3. The data is retrieved and submitted to the user

• The parsing process comprises six main tasks that ensure the validity of the statement as well as the validity of the selected columns and determines the best method for retrieving the data


Summary Summary (continued)(continued) • The library cache is a major structure of the shared pool and is

used to store application code that is in use• The library cache is divided into pieces of memory structures

called namespaces• You can look at the library cache namespaces by displaying the

contents of the V$LIBRARYCACHE performance dynamic view

• You can use V$SESSION_OBJECT_CACHE to get a full statistics report on cached objects for the current session

oracle9 i performance tuning

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shared pool memoryuse

shared pool memoryunderstand

cached sql statement

shared pool memorypin

submitted sql statement

major memory space

plsql blocks data

privilegesjava code