Note 1289199 - Information About Oracle Parameters

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SAP Note 1289199 - Information about Oracle parameters

Note Language: English Version: 9 Validity: Valid Since 26.07.2011

Summary

SymptomYou require more information about certain Oracle parameters.

Other terms

Reason and PrerequisitesThis note provides descriptions and background information about certainOracle parameters.

See Note 830576 for recommended parameter settings when using Oracle 10g.

Solution

o BACKGROUND_DUMP_DEST

- Path for alert log and background trace files

o COMPATIBLE

- Defines the Oracle version whose features can be used to thegreatest extent

- As a rule, it must not be reset to an earlier release (see Note598470).

- A value with three parts (such as 10.2.0) rather than fiveparts (such as 10.2.0.2.0) is recommended to avoid changing theparameter as part of a patch set installation.

- If an ORA-00201 error occurs when you try to convert the valuewith five parts 10.2.0.2.0 to 10.2.0, you can leave the value10.2.0.2.0 (independent of the patch set used).

o CONTROL_FILES

- Path and name of the control files that are used

o CONTROL_FILE_RECORD_KEEP_TIME

- Defines how many days historic data is retained in the controlfiles

- Historic data is required by RMAN, for example.

- May cause control files to increase in size (see Note 904490)

o CORE_DUMP_DEST

- Path under which core files are stored

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o DB_BLOCK_SIZE.

- Size of an Oracle block

- Can be set to a value higher than 8K in well-founded individualcases after it has been approved by SAP Support (see Note105047)

o DB_CACHE_SIZE

- Size of the Oracle data buffer (in bytes)

- Optimal size depends on the available memory (see Notes 789011and 617416)

o DB_FILES

- Maximum number of Oracle data files

o DB_NAME

- Name of the database

o DB_WRITER_PROCESSES

- Number of DBWR processes

o EVENT

- Activation of internal control mechanisms and functions

- To set events in SPFILE, refer also to Note 596423.

- If many events are set, data sources such as V$PARAMETER,DBA_HIST_PARAMETER, or "SHOW PARAMETER" may supply anincomplete value. This is only a display problem. The valuesthat are included in V$PARAMETER2 are the relevant values.

o FILESYSTEMIO_OPTIONS

- Activation of file system functions (see Note 999524 and Note793113)

- If you previously used a large file system cache (>= 2 * OracleBuffer Pool), the performance may get worse after you activatedthe direct I/O if you set FILESYSTEMIO_OPTIONS to SETALL.Therefore, it is important that you enlarge the Oracle bufferpool to replace the file system cache that is no longeravailable.

o HPUX_SCHED_NOAGE

- Optimized scheduling policy for Oracle processes on HP-UX.

- The privileges RTSCHED and RTPRIO must be assigned to the dbagroup to enable you to use the functions (see Note 1285599).

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o LOG_ARCHIVE_DEST

- Historic variant of LOG_ARCHIVE_DEST_1, which is not compatiblewith features such as the Flash Recovery Area and which shouldtherefore no longer be used.

o LOG_ARCHIVE_DEST_1

- Path/prefix for offline redo logs

- The syntax differs with an additional "LOCATION=" string ofLOG_ARCHIVE_DEST; if this difference is ignored, ORA-16024occurs concerning LOG_ARCHIVE_DEST_1.

o LOG_ARCHIVE_FORMAT

- Name format of the offline redo logs

- To avoid the problems described in Note 132551, it must beexplicitly set to WINDOWS at least.

o LOG_BUFFER

- Minimum size of the Oracle redo buffer (in bytes)

- Oracle internally determines the buffer's actual size, so it isnormal for "SHOW PARAMETER LOG_BUFFER" or a SELECT onV$PARAMETER to return values between 1MB and 16MB.

o LOG_CHECKPOINTS_TO_ALERT

- Defines whether checkpoints are to be logged in the alert log

o MAX_DUMP_FILE_SIZE

- Maximum size of Oracle trace files (in operating system blocks)

- A limitation is useful to avoid file system overflows and toreduce the duration of the dump generation.

- You can increase it temporarily if required.

o OPEN_CURSORS

- Maximum number of cursors opened in parallel by one session

o OPTIMIZER_DYNAMIC_SAMPLING

- Determines how much data is to be read to determine the accessplan.

- Level 2 (the default setting for Oracle 10g): Dynamic samplingis performed only if tables do not have any statistics.

- Level 6: As level 2 and includes dynamic sampling of 128 tableblocks if literals are used and there are no bind variables.

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o OPTIMIZER_INDEX_COST_ADJ

- Adjusts the calculated index costs; when there is a value of 20(percent), index costs are reduced by a factor of 5, forexample.

- A value lower than 100 is advisable so that index accesses arepreferred instead of full table scans.

o PARALLEL_EXECUTION_MESSAGE_SIZE

- Defines size of the memory area for parallel query messages (inbytes)

o PARALLEL_MAX_SERVERS

- Defines the maximum number of parallel execution processes (seeNote 651060)

- Based on the number of CPU Cores of the database server

- The number of CPU Cores generally corresponds to the defaultvalue for the Oracle parameter CPU_COUNT. If you are unsure inindividual cases, you can use the value of the parameterCPU_COUNT (for example, in transaction DB26).

- If the database shares the server with other software (forexample, SAP central instance, other Oracle instances), you canalso select a lower value (for example, 8 CPU Cores, the SAPcentral instance and the Oracle database should share resources50:50 -> PARALLEL_MAX_SERVERS = 8 * 0.5 * 10 = 40).

o PARALLEL_THREADS_PER_CPU

- Defines the number of parallel query processes that can beexecuted in parallel for each CPU

- Influences the DEFAULT level of parallel processing during aparallel execution (see Note 651060).

o PGA_AGGREGATE_TARGET

- Checks the available PGA memory (see Notes 789011 and 619876)

o PROCESSES

- Defines the maximum number of Oracle processes that exist inparallel

- The component relating to ABAP work processes is only relevantin systems with ABAP stacks. The component relating to J2EEserver processes is only relevant in systems with Java stacks.

- <max-connections> indicates the maximum number of connections(also called pool size) of the J2EE system DataSource(sysDS.maximumConnections). You can set the value of thisparameter using the VisualAdmin tool or other J2EE

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administration tools.

o QUERY_REWRITE_ENABLED

- Defines whether query transformations are also factored in whenthe access path is determined

o RECYCLEBIN

- Enables access later on to objects that have already beendropped

- Not supported by SAP (see Note 105047)

o REMOTE_OS_AUTHENT

- Defines whether TCP database access via OPS$ users is allowed(see Note 400241)

o REPLICATION_DEPENDENCY_TRACKING

- Defines whether the system has to create replicationinformation when the database is accessed

- Performance improves if it is deactivated

o SESSIONS

- Defines the maximum number of Oracle sessions that exist inparallel - must be configured larger than PROCESSES, sincesingle processes can serve several sessions (for example, inthe case of multiple database connections from work processes)

o SHARED_POOL_SIZE

- Defines the size of the Oracle shared pool (see Notes 690241and 789011)

o STAR_TRANSFORMATION_ENABLED

- Specifies to what extent STAR transformations can be used

o UNDO_MANAGEMENT

- Defines whether automatic undo management is used (see Note600141)

o UNDO_TABLESPACE

- Defines the undo tablespace to be used (see Note 600141)

o USER_DUMP_DEST

- Path for trace files of Oracle shadow processes

o _B_TREE_BITMAP_PLANS

- Defines whether data of a B*TREE index can be transformed into

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a bitmap display during a database access.

o _BLOOM_FILTER_ENABLED

- Determines whether bloom filters may be used during joins.

o _DB_BLOCK_NUMA

- Control use of NUMA optimizations.

o _ENABLE_NUMA_OPTIMIZATION

- Control use of NUMA optimizations.

o _FIX_CONTROL

- Activates or deactivates individual CBO fixes

- To set _FIX_CONTROL, see Note 1455168.

- If many _FIX_CONTROL values are set, data sources such asV$PARAMETER, DBA_HIST_PARAMETER, or "SHOW PARAMETER" may supplyan incomplete value. This is only a display problem. The valuesthat are included in V$SYSTEM_FIX_CONTROL are the relevantvalues.

- Note 1454675 describes a problem whereby the _FIX_CONTROLvalues do not work despite being displayed correctly inV$PARAMETER.

o _CURSOR_FEATURES_ENABLED

- With a value of 10 and in connection with fix 6795880, thefollowing is prevented: sporadic hanging during parsing

o _FIRST_SPARE_PARAMETER

- This is a generic parameter that can be used for differentpurposes in certain cases.

- With Oracle 10.2.0.4 and fix 6904068, you use this parameter tointroduce a break of 1/100 second between two "cursor: pin S"mutex requests instead of continually executing requests. Thismay help to avoid critical CPU bottlenecks.

o _INDEX_JOIN_ENABLED

- Controls whether index joins can be used or not; within anindex join, two indices of a table are directly linkedtogether.

o _IN_MEMORY_UNDO

- Controls whether the In Memory Undo feature (IMU) is used ornot

o _OPTIM_PEEK_USER_BINDS

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- Defines whether Oracle takes the contents of the bind variablesinto account during parsing

- May cause various problems (Notes 755342, 723879) if not set toFALSE.

o _OPTIMIZER_BETTER_INLIST_COSTING

- Controls the cost calculation for IN lists

- If the parameter is set to OFF, long IN lists are evaluatedvery favorably.

- The CBO performs a reasonable cost calculation for IN listsusing the value ALL.

- Therefore, you should always use the default value ALL (thismeans that you should not set the parameter). If the CBO takesincorrect decisions in individual cases, these incorrectdecisions must be analyzed and corrected.

o _OPTIMIZER_MJC_ENABLED

- Controls whether Cartesian merge joins are used.

o _PUSH_JOIN_UNION_VIEW

- Controls whether join predicates may be used in a UNION ALLconstruct beyond the view boundaries.

o _SORT_ELIMINATION_COST_RATIO

- Controls rule-based CBO decision in connection with theFIRST_ROWS hint and ORDER BY (see Note 176754).

o _TABLE_LOOKUP_PREFETCH_SIZE

- Controls whether table prefetching is used (a value of zeromeans no table prefetching).

Header Data

Release Status: Released for CustomerReleased on: 26.07.2011 15:00:23Master Language: GermanPriority: Recommendations/additional infoCategory: ConsultingPrimary Component: BC-DB-ORA Oracle

The Note is release-independent

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Related Notes

Number Short Text

1455168 _FIX_CONTROL syntax

1454675 _FIX_CONTROL parameters are ignored

830576 Parameter recommendations for Oracle 10g

Note 1289199 - Information About Oracle Parameters

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