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Background documentation Special Database Parameters (Extended) Locate the document in its SAP Library structure

The following parameters are database parameters that specify special database properties:

_EVENT_ALIVE_CYCLE

The time in seconds of an event cycle

_MAX_MESSAGE_FILES

Maximum number of trace files that can be open simultaneously

_MAXEVENTS

Maximum number of events stored by the kernel in the cache for processing by the Database Manager

_UNICODE

Parameter for creating a UNICODE-compliant database

Note

You can no longer change this database parameter after you have created the database instance.

CAT_CACHE_SUPPLY

Size of catalog cache memory for all user tasks in pages

DATE_TIME_FORMAT

System default for the date and time format

DEADLOCK_DETECTION

Maximum search level for deadlock detection.

Any deadlocks that are not detected at this search level are only resolved by the parameter REQUEST_TIMEOUT.

If DEADLOCK_DETECTION = 0, deadlock detection is disabled.

DEFAULT_CODE

Determines the default code attribute of the database instance. This default is then used for saving the column values of the data types CHAR[ACTER], VARCHAR, and LONG[VARCHAR].

DEVNO_BIT_COUNT

See DEVNO_BIT_COUNT

DIAG_HISTORY_NUM

Number of histories in the <diag_history_path> directory

DIAG_HISTORY_PATH

Directory <diag_history_path> for the histories of log files

The default value is DIAGHISTORY in the run directory of the database instance.

JOIN_MAXTAB_LEVEL4

Threshold value for the number of tables in a join for selecting the join sequence algorithm.

JOIN_MAXTAB_LEVEL9

Threshold value for the number of tables in a join for selecting the join sequence algorithm.

JOIN_SEARCH_LEVEL

see JOIN_SEARCH_LEVEL

KERNELDIAGSIZE

Size of the log file knldiag in KB

LOG_BACKUP_TO_PIPE

Specifies whether log backup in pipes is permitted

LOG_IO_QUEUE

Size of the log queue in pages

LRU_FOR_SCAN

Specifies whether the entire data cache is used for scans

MAXRGN_REQUEST

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

If this number is exceeded, the task lets another task access the CPU as long as it belongs to the same user kernel thread.

MAXSERVERTASKS

Determines the number of server tasks that are available, for example, for backups and restores

MP_RGN_LOOP

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

If this number is exceeded, the accessing task changes its status “Waiting”.

OPTIM_INV_ONLY

Determines whether the Index Only strategy is used for joins

OPTIM_MAX_MERGE

Specifies the change of the optimizer algorithm of the strategies for merging index lists

If the number of pages of an index that need to be merged exceeds the value specified in OPTIM_MAX_MERGE, this index will not be used for an index merging strategy.

REQUEST_TIMEOUT

Maximum wait before a lock is released (in seconds)

This database parameter limits the amount of time you have to wait until a lock is released by other users for all database sessions.

If a lock request cannot be satisfied within the time defined here, a message is returned to the waiting database session. Any changes made previously in the transactions are undone.

SEQUENCE_CACHE

The size of the sequence cache in pages

SESSION_TIMEOUT

Timeout value  for database sessions in seconds

UTILITY_PROT_SIZE

Size of the log file dbm.utl in pages

Note

You can display the full list of special database parameters for your database instance and additional information about these parameters using the Database Manager.

 

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