AutoLogBackupSize

LOG_SEGMENT_SIZE

Log segment size (in pages)

When automatic log backup is activated and no time interval has been configured, then the database system starts an automatic log backup as soon as a log segment is full.

0: system uses 1/3 of the log area as the log segment size

≤50% of the log area: system uses the value defined in AutoLogBackupSize

> 50% of the log area: system uses 50% of the log area as the log segment size

Changes only apply after a restart of the database.

Database Administration, Backing Up Log Entries

BridgeType

-

Specifies whether the database is used in a bridge scenario (where the database acts as a bridge to other databases)

Changes only apply after a restart of the database.

CacheMemorySize

CACHE_SIZE

Size of the working memory (RAM) which is used by the database system for I/O operations (in pages).

The main consumers of the working memory area configured with CacheMemorySize are the data cache, the converter, the shared catalog cache and the file directory; but other database components also use this memory area.

The following restrictions apply: 800 ≤ CacheMemorySize < total RAM size

This parameter has a great impact on the performance of your system. The optimum value for this parameter depends on your system environment. Note that other database functions and programs also need a certain amount of working memory, so do not assign your whole working memory to CacheMemorySize.

Changes only apply after a restart of the database.

Database Administration, Analyzing Database Performance

Concepts of the Database System, Working Memory Areas

InstanceType

INSTANCE_TYPE

Database type:

You define the database type when you create the database.

Cannot be changed

Concepts of the Database Systems,

KernelVersion

KERNELVERSION

Version of the database software

You cannot change this value.

When you install a new version of the database software, the database system updates the value of this parameter.

MaxBackupMedia

MAXBACKUPDEVS

Maximum number of files or tape devices for parallel backup

Changes only apply after a restart of the database.

Database Administration, Backup Templates and Data Carriers

MaxCPUs

MAXCPU

Maximum number of processors to which the database system can distribute user tasks.

When choosing this value, bear in mind that your computer's operating system resources have to be available for other programs as well.

To further restrict the number of available CPUs in a running system, use the special database parameter UseableCPUs.

Changes only apply after a restart of the database.

SAP Note 936058

MaxDataVolumes

MAXDATAVOLUMES

Maximum number of data volumes

Changes only apply after a restart of the database.

Concepts of the Database System, Volumes (Permanent Storage)

MaxLogVolumes

MAXLOGVOLUMES

Maximum number of log volumes

Changes only apply after a restart of the database.

MaxSQLLocks

MAXLOCKS

Maximum number of locks for database objects

Changes only apply after a restart of the database.

Concepts of the Database System, Locks

MaxUserTasks

MAXUSERTASKS

Maximum number of simultaneously active user tasks and therefore the maximum number of database sessions

If this number has been reached, then no additional user can log on to the database.

Note that if you choose a large value for MaxUserTasks, the database system requires much address space, particularly for local communication via shared memory.

For SAP systems (OLTP), we recommend the following minimum value: 2 x <number_of_SAP_processes> + 4

Changes only apply after a restart of the database.

Concepts of the Database System, Tasks

SAP Note 757914

MCODIndicator

MCOD

MCOD = Multiple Components One Database

In SAP systems, this parameter indicates whether several applications are using this database.

Changes only apply after a restart of the database.

OmsMaxHeapSize

OMS_HEAP_LIMIT

For SAP liveCache databases

Specifies the maximum size of the OMS heap (in KB)

Changes only apply after a restart of the database

-

RunDirectoryPath

RUNDIRECTORY

Run directory of the database

If you specify a relative path, the system interprets this path relative to the data path:

<global_data_path>\wrk\<database_name>\ or<private_data_path>\wrk\<database_name>\ (if you have configured a private data path during installation)

Changes only apply after a restart of the database.

Glossary, Run Directory

UseMirroredLog

LOG_MIRRORED

Specifies whether the database system mirrors the log area (software-based mirroring)

This parameter is relevant only when you create a mirror volume using Database Manager CLI. Database Studio automatically adjusts this parameter when you create a mirror volume.

Note that it we recommend to use hardware-based mirroring for the log area. More information: Planning Databases

Changes only apply after a restart of the database.

Glossary, Log Mode

AllowAuthentication

AUTHENTICATION_ALLOW

Specifies the authentication methods that are allowed for the database. Possible Values (comma-separated):

If you do not specify a value, then all authentication methods are allowed except those specified using the database parameter DenyAuthentication.

Can be changed in ONLINE or ADMIN operational state

CAT_CACHE_SUPPLY

CAT_CACHE_SUPPLY

Size of the task-specific catalog cache in the working memory that is allocated to user tasks (in pages)

For each user task the system reserves a minimum part of the catalog cache (see TaskSpecificCatalogCacheMinSize). Each task may extend its catalog cache, but all task-specific catalog caches together may not exceed the catalog cache size. Note that the catalog cache size influences performance: You achieve the best performance with a catalog cache hit rate of 100%. Use database monitoring to get information about the catalog cache hit rate.

Changes only apply after a restart of the database.

Concepts of the Database System, Working Memory Areas

ClusterWriteThreshold

CLUSTER_WRITE_THRESHOLD

Minimum amount of blocks that the database system still stores as clusters in the data area

Can be changed in ONLINE or ADMIN operational state

-

ClusterCompressionFillThreshold

-

Maximum number of occupied blocks in clusters eligible for compression

If more blocks are occupied in a cluster, the database system does not compress the cluster.

Can be changed in ONLINE or ADMIN operational state

-

ConverterStripes

CONVERTER_REGIONS

Number of critical sections into which the converter is divided

This division enables parallel writing to the converter.

The default value is calculated by the database system. You can change the value. Changes only apply after a restart of the database.

Glossary, Stripe

ConverterVolumeIdLayout

VOLUMENO_BIT_COUNT

Number of bits in the converter block address that are reserved for the logical volume number of a data volume

We recommend that you do not change the value that was defined when the database was created. If you change the database parameter in the ONLINE or ADMIN operational state, you must restore the database afterwards to update the numbering of the data volume.

Database Administration, Planning the Database

DataCacheStripes

_DATA_CACHE_RGNS

Number of critical sections into which the data cache is divided

This division enables parallel writing to the data cache.

The default value is calculated by the database system. You can change the value. Changes only apply after a restart of the database.

DateTimeFormat

DATE_TIME_FORMAT

System default for the date and time format

You can override this date and time format when using database tools (standard_date_mask in Loader) or when using SQL statements (datetimeformat).

Can be changed in ONLINE or ADMIN operational state

-

DeadlockDetectionLevel

DEADLOCK_DETECTION

Maximum search level for deadlock detection

Any deadlocks that the database system does not detect at this search level are only resolved by a timeout.

Can be changed in ONLINE or ADMIN operational state

Parameter RequestTimeout

DefaultCodePage

DEFAULT_CODE

System default for the code attribute, applies only to the column values of the data types CHAR[ACTER], VARCHAR and CLOB

Can be changed in ONLINE or ADMIN operational state

SQL Reference Manual, Code Attribute

DenyAuthentication

AUTHENTICATION_DENY

Specifies the authentication methods that are not allowed for this database. Possible Values (comma-separated):

Note that older clients can only connect to the database using the BASIC authentication method. Not allowing this method prevents these clients from being able to connect.

Can be changed in ONLINE or ADMIN operational state

n

DiagnoseHistoryCount

DIAG_HISTORY_NUM

Number of history versions in the directory in which the database system stores diagnosis files (backups of the most important log files and memory dumps) after a database error

Changes only apply after a restart of the database.

Database Administration, Log Files

DiagnoseHistoryPath

DIAG_HISTORY_PATH

Directory in which the database system stores diagnosis files (backups of the most important log files and memory dumps) after a database error

Changes only apply after a restart of the database.

See above

EnableIndexOnlyStrategy

OPTIM_INV_ONLY

Defines whether the SQL optimizer uses the Index Only strategy for joins

Can be changed in ONLINE or ADMIN operational state

SQL Optimizer, Search Strategies

EnableLogBackupToPipe

LOG_BACKUP_TO_PIPE

NO: After a log backup has been written to a pipe, the connection to the pipe is closed. The system does not receive any information on whether the log backup was successful. As a result, the log area is not released and cannot be overwritten. Therefore, it may become full. Consequently no changes to data can be made any more.

YES: The database system can overwrite the log entries in the log area that have already been written to the pipe. Note that the system does not check whether the log backup to the pipe was successful.

Changes only apply after a restart of the database.

Database Administration, Backing Up Log Entries

EnableQueryRewrite

OPTIMIZE_QUERYREWRITE

Prerequisite: Support database parameter QueryAnalysisMode is set to EXTENDED.

Specifies whether the system tries to transform SQL statements so that the resulting statement is semantically identical but faster to process. The transformations are purely rule-based and do not take into account any statistical information. The main purpose of transformations is to avoid intermediate result sets.

In some cases, it may not be possible to display the statement that results from the transformation as an SQL statement.

After an SQL statement has been transformed, the SQL optimizer determines the most cost-effective search strategy for accessing the data.

The system can transform the following types of SQL statements: SELECT, CREATE CURSOR FOR SELECT, EXPLAIN SELECT

After the system has transformed an SQL statement, the result of the EXPLAIN statement contains the text QUERY REWRITE DONE as well as a list indicating the rules executed and the number how often they were executed.

Can be changed in ONLINE or ADMIN operational state

-

ExclusiveLockRescheduleThreshold

MAXRGN_REQUEST

Maximum number of attempts a task should make to access a critical section

If this number is exceeded, the task releases its access to the CPU. The CPU can then be accessed by another task belonging to the same user kernel thread.

Can be changed in ONLINE or ADMIN operational state

Glossary, Critical Section

FileDirectorySpinlockPoolSize

FILEDIR_SPINLOCKPOOL_SIZE

Number of spinlocks available for reader-writer locks for the internal file directory

Changes only apply after a restart of the database.

Glossary, Reader-Writer Lock

FormatDataVolume

FORMAT_DATAVOLUME

Only for test purposes

Suppresses the formatting of data volumes when a new database is created

Changes only apply after a restart of the database.

Glossary, Volume

HashJoinSingleTableMemorySize

MAX_SINGLE_HASHTABLE_SIZE

Maximum size of the working memory that the database system can use to cache a single table when executing a join (in KB)

Can be changed in ONLINE or ADMIN operational state

See above

HashJoinTotalMemorySize

MAX_HASHTABLE_MEMORY

Maximum size of the working memory that the database system can use to cache all tables when executing joins (in KB)

Can be changed in ONLINE or ADMIN operational state

Glossary, Join

HighResolutionTimer

HIRES_TIMER_TYPE

Type of time measurement that is used by the kernel for internal operations

Use this parameter only for multiprocessor computers on which there could be synchronization problems between the CPUs.

Changes only apply after a restart of the database.

-

HotStandbyDelayTime?

HS_DELAY_TIME_<NNN>

Delay in seconds after which the standby database applies the data changes of the master database. The question mark (?) is used as placeholder for the three-digit identification of the standby database.

Changes only apply after a restart of the database.

Database Administration, Hot Standby

HotStandbyNodeName?

HS_NODE_<NNN>

Only for hot standby systems

Host name or IP address of the database The question mark (?) is used as a placeholder for the three-digit identification of the database. The default value for the master database is HotStandbyNodeName001.

Changes only apply after a restart of the database.

See above

HotStandbyStorageDLLPath

HS_STORAGE_DLL

Only for hot standby systems

Name of the library through which the system addresses the memory management system

The default value is libhsscopy.

Changes only apply after a restart of the database.

See above

HotStandbySyncInterval

HS_SYNC_INTERVAL

Only for hot standby systems

Minimum time span between two commands of the master database to synchronize the standby databases (in s)

Changes only apply after a restart of the database.

See above

IndexListsMergeThreshold

OPTIM_MAX_MERGE

Specifies whether the SQL optimizer uses an index-merge strategy

If the number of pages of an index that need to be merged exceeds the value specified in IndexListsMergeThreshold, the SQL optimizer does not use this index for an Index Merge strategy.

Can be changed in ONLINE or ADMIN operational state

SQL Optimizer, Search Strategies

JoinSearchLevel

JOIN_SEARCH_LEVEL

Algorithm used by the SQL optimizer for the join sequence search

Can be changed in ONLINE or ADMIN operational state

SQL Optimizer,

Database Parameter JoinSearchLevel

JoinSearchTableThreshold4

JOIN_MAXTAB_LEVEL4

Parameter of the SQL optimizer

Can be changed in ONLINE or ADMIN operational state

JoinSearchLevel

JoinSearchTableThreshold9

JOIN_MAXTAB_LEVEL9

Parameter of the SQL optimizer

Can be changed in ONLINE or ADMIN operational state

JoinSearchLevel

JoinTableBufferSize

JOIN_TABLEBUFFER

Size of the buffer (in KB) per user task for table buffers used during join execution

Can be changed in ONLINE or ADMIN operational state

SQL Optimizer, Search Strategies for Joins

KernelMessageFileSize

KERNELDIAGSIZE

Size of the kernel log file (in KB)

Changes only apply after a restart of the database.

Database Administration, Log Files

KernelMessageHistoryCount

KNLMSG_HISTORY_NUM

Number of stored old kernel log files

At each database start, the system moves the old kernel log file to the log history directory.

Changes only apply after a restart of the database.

Database parameter DiagnoseHistoryPath

MaxKernelMessageArchiveSize

-

If this parameter is set to a value other than 0, it defines the maximum size of the KnlMsgArchive file (containing archived messages of the database kernel).

If the specified size is reached, the system renames the KnlMsgArchive file to KnlMsgArchive_<timestamp> and creates a KnlMsgArchive file.

Can be changed in ONLINE or ADMIN operational state

LoadBalancingCheckInterval

LoadBalancingCheckLevel

LOAD_BALANCING_CHK

Time interval in which the database system checks whether it should use load balancing (in s)

Can be changed in ONLINE or ADMIN operational state

Concepts of the Database System, Load Balancing between User Kernel Threads

LocalRedoLogBufferSize

LOCAL_REDO_LOG_BUFFER_SIZE

If you enter a value > 0, then the system allocates a local buffer of this size (in bytes) to each transaction for saving redo log entries.

Changes only apply after a restart of the database.

-

LogQueues

LOG_QUEUE_COUNT

Number of log queues

If this number is 0, the system calculates the number from the parameter MaxLogQueues

Changes only apply after a restart of the database.

Glossary, Log Queue

LogQueueSize

LOG_IO_QUEUE

Size of the individual log queues (in pages)

Changes only apply after a restart of the database.

See above

MaxEvents

_MAXEVENTS

Maximum number of events in the working memory that can be processed by the system

Changes only apply after a restart of the database.

Glossary, Event

MaxExclusiveLockCollisionLoops

MP_RGN_LOOP

Maximum number of times a task attempts to access a critical section that has been locked by another task

If this number is exceeded, the accessing task changes its state to Waiting.

Can be changed in ONLINE or ADMIN operational state

Glossary, Critical Section

MaxLogWriterTasks

MAX_BACKUP_TASKS

Maximum number of log writer tasks (determines the maximum number of log partitions)

Changes only apply after a restart of the database.

Concepts of the Database System, Log Area and Tasks

MaxMemoryAllocationSize

MEMORY_ALLOCATION_LIMIT

Maximum amount of working memory to be used by the database (in KB)

Can be changed in ONLINE or ADMIN operational state

-

MaxParallelLiveCacheTraceFiles

_MAX_MESSAGE_FILES

Maximum number of trace files that the system can open simultaneously

Changes only apply after a restart of the database.

-

MaxRetentionTime

MinRetentionTime

MAX_RETENTION_TIME

MIN_RETENTION_TIME

For SAP liveCache databases

Specifies the time (in min) after which the garbage collectors start deleting the history data (undo log entries and links to them)

The garbage collectors start deleting the history data in the following cases:

Can be changed in ONLINE or ADMIN operational state

Concepts of the Database System, How Databases Log Data Changes

MaxServerTasks

MAXSERVERTASKS

Maximum number of server tasks

Changes only apply after a restart of the database.

Concepts of the Database System, Tasks

OfficialNodeName

OFFICIAL_NODE

Only for hot standby systems

Virtual Server Name by which the cluster is addressed from the outside

The system administrator initially assigns the Virtual Server Name to the computer on which the master database of the hot standby system is located.

If the master database fails, then the name transfers to the standby database that takes on the master role.

Changes only apply after a restart of the database.

Glossary, Hot Standby

OmsHeapThreshold

OMS_HEAP_THRESHOLD

For SAP liveCache databases

Specifies how much working memory usage the OMS heap may use (in %)

Changes only apply after a restart of the database

-

OmsSubHeaps

OMS_HEAP_COUNT

For SAP liveCache databases

Specifies whether the OMS heap is divided into segments

If the OMS heap is not divided into segments, the internal heap memory management locks the entire OMS heap whenever a database procedure requests or releases memory.

Changes only apply after a restart of the database

Concepts of the Database System, Working Memory Areas

OmsVersionThreshold

OMS_VERS_THRESHOLD

For SAP liveCache databases

Specifies how much working memory the OMS versions may use (in KB)

Changes only apply after a restart of the database

-

RequestTimeout

REQUEST_TIMEOUT

Maximum time that a database session waits for a locked database object to be released (in s)

If this time is exceed, the system sends a message to the waiting database session. The system then rolls back any changes that were previously executed within the respective transaction.

Changes only apply after a restart of the database.

Concepts of the Database System, Locks

RequestUpdateStatisticsThreshold

-

If the system detects that the size of a table has changed by more than the value specified in this parameter (in percent) since the last statistics update, it marks the table as needing a statistics update.

Can be changed in ONLINE or ADMIN operational state

RowLockManagementStripes

_ROW_RGNS

Number of critical sections into which the row lock list is divided

This division enables a parallel access to the lock list.

Changes only apply after a restart of the database.

Glossary, Critical Section

RowLocksPerTransactionThreshold

-

Maximum percentage of all available locks that a transaction can hold before the system attempts a lock escalation.

Can be changed in ONLINE or ADMIN operational state

Glossary, Lock

SequenceCacheSize

SEQUENCE_CACHE

Size of the sequence cache (in pages)

Changes only apply after a restart of the database.

Glossary, Sequence Cache

SessionTimeout

SESSION_TIMEOUT

Timeout value for database sessions (in s)

Can be changed in ONLINE or ADMIN operational state

Glossary, Database Session

SharedSQLCleanupThreshold

SHAREDSQL_EXPECTEDSTATEMENTCOUNT

Expected number of SQL statements to be stored in the shared SQL cache

Can be changed in ONLINE or ADMIN operational state

-

SharedSQLCommandCacheSize

SHAREDSQL_COMMANDCACHESIZE

Maximum size of the Shared SQL cache (in KB)

Can be changed in ONLINE or ADMIN operational state

-

TableLockManagementStripes

_TAB_RGNS

Number of critical sections into which the table lock list is divided

This division enables a parallel access to the lock list.

Changes only apply after a restart of the database.

Glossary, Critical Section

TraceBufferSize<task_type>Task

TRACE_PAGES_<task_type>

Each user kernel thread has its own trace area in the working memory.

This parameter specifies the maximum number of pages that are available to the specified task type per user kernel thread.

<task_type>:BUP (Backup Task, not yet implemented)|FS (Floating Service Task: either an event task or a Database Analyzer task)|GC (Garbage Collector)|LW (Log Writer)|PG (Pager)|SV (Server Task)|TI (Timer Task)|US (User Task)|UT (Utility Task)

Changes only apply after a restart of the database.

Concepts of the Database System, Tasks

TransactionHistorySize

TRANS_HISTORY_SIZE

Specifies for how many long-running transactions the system stores information

Changes only apply after a restart of the database.

-

TransactionHistoryThreshold

TRANS_THRESHOLD_VALUE

Time (in s) after which a transaction is considered long-running by the system

Can be changed in ONLINE or ADMIN operational state

-

TransactionLockManagementStripes

_TRANS_RGNS

Number of critical sections into which the transaction lock list is divided

This division enables a parallel access to the lock list.

Changes only apply after a restart of the database.

Glossary, Critical Section

UpdateStatSampleAlgorithm

UPDATESTAT_SAMPLE_ALGO

Determines the algorithm that the database system uses to update the SQL optimizer statistics

In SAP systems we recommend the value 1 for this parameter.

Can be changed in ONLINE or ADMIN operational state

SQL Optimizer, SQL Optimizer Statistics

UseableCPUs

-

Restricts the number of available CPUs in a running system.

The following constraint applies:1 ≤ UseableCPUs ≤ MaxCPUs

To permanently configure the number of available CPUs, use the general database parameter MaxCPUs.

Can be changed in ONLINE or ADMIN operational state

UseBackupSecurityDescriptor

USE_BACKUP_SECURITY_DESCRIPTOR

Only on Microsoft Windows

Specifies whether the system uses the Microsoft Windows Security Descriptor for backups to data carriers of the file type

Changes only apply after a restart of the database.

-

UseDataCacheScanOptimization

LRU_FOR_SCAN

Specifies whether the whole data cache is used for scans

Can be changed in ONLINE or ADMIN operational state

-

UseHashedResultset

HASHED_RESULTSET

Specifies whether the SQL optimizer uses temporary hash tables for creating aggregations.

Can be changed in ONLINE or ADMIN operational state

UseLobClustering

CLUSTERED_LOBS

Specifies whether the database system stores LOB values as clusters in the data area

Can be changed in ONLINE or ADMIN operational state

-

UseSharedSQL

SHAREDSQL

Activates the Shared SQL function

Parameter can be activated in ONLINE or ADMIN operational state but not deactivated

Glossary, Shared SQL

UseUnicodeColumnCompression

-

Specifies whether the system stores application data in columns of the type (VAR)CHAR UNICODE in newly created tables as UTF8

Can be changed in ONLINE or ADMIN operational state

Glossary, Data Type

VolumeFormattingMode

FORMATTING_MODE

The database system formats the volumes when the database is created. With this parameter, you specify the formatting type. Only use parallel formatting for data volumes of the FILE type that are located on different hard disks.

Changes only apply after a restart of the database.

Glossary, Volume

CommandBufferSize

_PACKET_SIZE

Size of the packages (shared memory segments) in which SQL statements and data are transferred

A package consists of a request part and a reply part.

The minimum package size is 48 KB.

Changes only apply after a restart of the database.

-

DataIOClusterSize

DATA_IO_BLOCK_COUNT

Block size that the database system uses when writing data pages from the data cache to the data area.

The optimum block size depends on your hardware and software.

Changes only apply after a restart of the database.

-

DeadlockDumpFileName

DEADLOCK_DUMP_FILENAME

Determines whether the system writes a dump file when it encounters an SQL deadlock situation

If you do not specify a file name, the system does not write a dump file.

If you specify a file name, the system writes a dump file with that name in the database run directory.

Note that the dump file can only be analyzed by development support.

Can be changed in ONLINE or ADMIN operational state

EnableMultipleServerTaskUKT

ALLOW_MULTIPLE_SERVERTASK_UKTS

Specifies whether the database system distributes the server tasks to the available user kernel threads. Otherwise they all run in the same user kernel thread.

Changes only apply after a restart of the database.

-

EnableRemoveUndoOnTransactionEnd

-

YES: All undo files that are not needed for the history or for the garbage collectors are removed by the transactions themselves. This means that nearly all OLTP undo files will be removed at the end of a transaction.

NO: The undo files are removed by the garbage collectors.

Can be changed in ONLINE and ADMIN operational state

Concepts of the Database System, Working Memory Areas

EnableSymbolDemangling

SYMBOL_DEMANGLING

Specifies whether the database system carries out C/C++ demangling

Can be changed in ONLINE and ADMIN operational state

-

EnableVariableInput

EnableVariableOutput

USEVARIABLEINPUT

These parameters determine how the system transfers the content of variables between client and kernel.

The system either transfers the actual length of the content or the maximum possible length of the content. In the latter case, the system fills up the content up to the maximum length (depending on the data type).

Changes only apply after a restart of the database

-

EventFileName

_EVENTFILE

Name of the file in which the database system logs events

Changes only apply after a restart of the database.

Log Files

EventFileSize

_EVENTSIZE

Size of the file in which the database system logs events (in KB)

Changes only apply after a restart of the database.

-

FloatingServiceTasks

-

Maximal number of tasks in the floating service task pool

The floating service task pool contains tasks that the system can use for events and for Database Analyzer

You must configure at least 2 event tasks and 1 Database Analyzer task.

See also PreservedEventTasks and PreservedDBAnalyzerTasks

Changes only apply after a restart of the database.

Concepts of the Database Systems, Tasks

InitialAllocatorSize

INIT_ALLOCATORSIZE

Initial size of the working memory that is reserved at the start of a database session

Changes only apply after a restart of the database.

-

KernelDumpFileName

_KERNELDUMPFILE

Name and location of the dump file that is written by the kernel when the database crashes

The system writes the contents of the data cache and the converter to this file. Caution: This file may become very large. You can estimate the size of this file in the following way: CacheMemorySize + 10%.

Changes only apply after a restart of the database.

Parameter DIAG_HIST_NUM

KernelTraceFile

_KERNELTRACEFILE

Name and location of th file to which the kernel writes the database trace messages

The kernel only writes database trace messages if you previously activated the database trace.

Changes only apply after a restart of the database.

Concepts of the Database System, Load Balancing Between User Kernel Threads

LoadBalancingWorkloadDeviation

LOAD_BALANCING_EQ

For internal load balancing

Specifies which time delays the system should regard as equal when comparing waiting tasks (as a percentage)

Can be changed in ONLINE and ADMIN operational state

-

LoadBalancingWorkloadThreshold

LOAD_BALANCING_DIF

For internal load balancing

If the system considers moving a task from one user kernel thread to another, this parameter specifies the amount of time this task has to have waited longer than the longest waiting task in the target user kernel thread (as a percentage).

Can be changed in ONLINE and ADMIN operational state

-

LogIOClusterSize

LOG_IO_BLOCK_COUNT

Block size that the database system uses when writing log pages from the log queues to the log area

The optimum block size depends on your hardware and software.

Changes only apply after a restart of the database.

-

MaxPagerTasks

MAXPAGER

Maximum number of pagers

The system calculates this parameter from the MAXDATAVOLUMES parameter and other parameters.

Not changeable

You can override this parameter using the XP_MAXPAGER parameter.

-

MaxSavepointTimeInterval

_RESTART_TIME

Minimum time between two savepoints (in s)

This corresponds to the time that is required for a restart after a system crash.

Note that the database system always writes a savepoint in the following cases:

Changes only apply after a restart of the database.

-

MaxServerTaskStackSize

MAX_SERVERTASK_STACK

Maximum size of the stack that is used by the server tasks

Changes only apply after a restart of the database.

Server Task

MaxSpecialTaskStackSize

MAX_SPECIALTASK_STACK

Maximum size of the stack that is used by the special tasks (all tasks except user tasks and server tasks)

Changes only apply after a restart of the database.

-

MaxTaskStackSize

_MAXTASK_STACK

Size of the stack that is used by the user tasks

Changes only apply after a restart of the database.

User Task

MaxTempFilesPerIndexCreation

_IDXFILE_LIST_SIZE

Number of temporary result files when the system is creating an index using multiple server tasks (parallel indexing)

The database system indexes large tables using multiple server tasks. These server tasks write their results to temporary files. When the number of these files reaches the value of this parameter, the database system has to merge the files before it can generate the actual index. This results in a decline in performance.

Can be changed in ONLINE and ADMIN operational state

-

OMSStreamTimeout

OMS_STREAM_TIMEOUT

Maximum wait time for all database sessions that may elapse until the reply to an OMS stream request from a client (in s)

Can be changed in ONLINE and ADMIN operational state

-

PreservedDBAnalyzerTasks

-

Minimum number of Database Analyzer tasks in the floating service task pool

See also FloatingServiceTasks

Changes only apply after a restart of the database.

Database Analyzer documentation

PreservedEventTasks

_MAXEVENTTASKS

Minimum number of event tasks in the floating service task pool

See also FloatingServiceTasks

The database system uses event tasks both for Event Dispatcher commands and for the DBM commands event_wait,event_receive, event_available, auto_extend and auto_update_statistics.

Changes only apply after a restart of the database.

Glossary, Event

QueryAnalysisMode

-

Specifies which internal mechanism is used for semantic analysis of queries.

To enable extended semantic analysis and as a prerequisite for the QueryRewrite function, choose EXTENDED.

Can be changed in ONLINE and ADMIN operational state

Special database parameter EnableQueryRewrite

ReadAheadLobThreshold

_READAHEAD_BLOBS

If a LOB value is too large to be transferred to the client in a single request package, the database system splits it into several request packages.

To increase performance, server tasks can import further parts of the LOB value while the first request package is being sent. This parameter specifies the minimum number of pages for a LOB value to be imported in advance by additional server tasks.

Can be changed in ONLINE and ADMIN operational state

-

RTEDumpFileName

_RTEDUMPFILE

Name of the file to which the kernel writes information about the runtime environment if the system crashes

Changes only apply after a restart of the database.

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ShowMaxStackUsage

SHOW_MAX_STACK_USE

Specifies whether the system logs the maximum stack usage of each task in the kernel log

Only set this parameter to YES for diagnosis purposes as it compromises performance.

Changes only apply after a restart of the database.

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TaskCluster01 to TaskCluster03

_TASKCLUSTER_01 to _03

These parameters determine how the database system distributes user tasks to the threads. Only change these parameters after consulting support.

Changes only apply after a restart of the database.

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TaskSpecificCatalogCacheMinSize

CAT_CACHE_MINSIZE

Minimum size of the task-specific catalog cache (in bytes)

Changes only apply after a restart of the database.

Concepts of the Database System, Working Memory Areas

UpdateStatParallelServerTask

UPDATESTAT_PARALLEL_SERVERS

Specifies how many parallel server tasks the database system uses for updating the SQL optimizer statistics

Can be changed in ONLINE and ADMIN operational state

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UseAsynchronousIO

_USE_ASYNC_IO

Specifies whether operating system functions or special I/O threads are used for asynchronous I/O operations

Changes only apply after a restart of the database.

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UseColumnCompression

COLUMNCOMPRESSION

Only for columns that are not primary key columns

Specifies whether the system can store the column values in variable length or not

Default value: YES (columns have variable length, so the values can be compressed if necessary)

Can be changed in ONLINE and ADMIN operational state

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UseExtendedOracleSQLMode

_SERVERDB_FOR_SAP

Specifies whether the database is being used in an SAP system

Can be changed in ONLINE and ADMIN operational state

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UseFilesystemCacheForBackup

-

Specifies whether the database system uses the operating system's file system cache for I/O operations (O_DIRECT flag) when opening volumes or data carriers for backup or restore

YES: The database system does not use the O_DIRECT flag

NO: The database system uses the O_DIRECT flag (if this flag is supported by the file system; note that this flag is ignored for Linux kernels < 2.4.18).

Changes only apply after a restart of the database.

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UseFilesystemCacheForVolume

(USE_OPEN_DIRECT)

Specifies whether the database system uses the operating system's file system cache for I/O operations O_DIRECT flag) when it is opening volumes for normal database operation

YES: The database system does not use the O_DIRECT flag

NO: The database system uses the O_DIRECT flag (if this flag is supported by the file system; note that this flag is ignored for Linux kernels < 2.4.18).

Changes only apply after a restart of the database.

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UseStrategyCache

OPTIM_CACHE

Specifies whether the database system determines the search strategy only once or every time it executes a parsed SQL statement

For prepared statements with parameters, it may be sufficient to determine the search strategy only once.

Can be changed in ONLINE and ADMIN operational state

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UseSystemPageCache

USE_SYSTEM_PAGE_CACHE

Specifies whether the database uses the system page cache for buffering memory pages that are no longer required

Changes only apply after a restart of the database.

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UseSystemTrigger

ENABLE_SYSTEM_TRIGGERS

Specifies whether system triggers are called when the database is restarted

Changes only apply after a restart of the database.

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UseVolumeLock

SET_VOLUME_LOCK

Specifies whether the database system sets a lock when a volume is added, which prevents the same volume from being added again later

In the following cases, it may make sense to set this parameter to NO:

Changes only apply after a restart of the database.

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