Special Database Parameters

AllowAuthentication

AUTHENTICATION_ALLOW

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

• SCRAMMD5: Challenge/response method using a MD5 hash algorithm

• BASIC: Passwords are sent using a reversible encryption algorithm

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 deadlock detection depth

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

Database parameter RequestTimeout

Deadlock

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):

• SCRAMMD5: Challenge/response method using a MD5 hash algorithm

• BASIC: Passwords are sent using a reversible encryption algorithm

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

Glossary, Join

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

See above

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>

Only for hot standby systems with a shared log area

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 System

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 link library for accessing the storage system

There is no default value. If no value is specified, the hot standby solution with separate log areas (no shared resources) is used.

Changes only apply after a restart of the database.

See above

HotStandbySyncInterval

HS_SYNC_INTERVAL

Only for hot standby systems with a shared log area

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

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:

• When the data area is more than 90% full, the garbage collectors delete all history data that is older than MinRetentionTime.

• When the data area is less than 90% full, the garbage collectors delete all history data that is older than MaxRetentionTime.

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

This name is used for addressing the hot standby system 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 is transferred to the standby database that takes on the master role.

Can be changed in ONLINE or ADMIN operational state

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

If this time is exceeded, 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, SQL 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

RowLocksPerTableThreshold

-

Maximum percentage of row locks that a transaction can set on a table before the system attempts a table lock escalation.

Can be changed in ONLINE or ADMIN operational state

Glossary, Lock

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

Defines the threshold (%) from which on clean up occurs within Shared SQL cache

Can be changed in ONLINE or ADMIN operational state

Glossary, Shared SQL

SharedSQLCommandCacheSize

SHAREDSQL_COMMANDCACHESIZE

Maximum size of the Shared SQL cache (in KB)

Can be changed in ONLINE or ADMIN operational state

See above

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> : PLW (Parallel Log Writer Task)| 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