Database parameters define the fundamental properties of a database. You can change the values of most database parameters.
Most changes to database parameters take effect only after the database has been restarted.
However, you can change individual database parameters while the database is running, that is in the ONLINE or ADMIN operational state (see the description of individual database parameters for more information). For these changes you can define when they are to become effective:
Until the next restart
After the next restart
Immediately and permanently
If you change a database parameter whose value is normally calculated by the system, then the system will consider this user-defined value for all subsequent recalculations of database parameter values. The system discards and recalculates this user-defined value only if it is not within the permitted value range (for example, after the database software has been updated).
Note
Starting with version 7.7.03 of the database software, the names of many database parameters have changed.
Some database parameters have also been designated obsolete. These parameters have either been removed already or will be removed in one of the next database versions.
More information: Obsolete Database Parameters
More information:
Database Administration, Database Parameters
Database Studio, Changing Database Parameters
Database Administration in CCMS, Parameters
Name (from version 7.7.03) |
Old Name (up to and including version 7.7.02) |
Description |
Change Restrictions |
More Information |
---|---|---|---|---|
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 makes 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 |
CacheMemorySize |
CACHE_SIZE |
Size of the I/O buffer cache = data cache + converter (in pages) If no value has been specified, the system calculates the value of this parameter as follows:
|
Changes only apply after a restart of the database |
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 When you install a new version of the database software, the database system updates the value of this parameter. |
Users cannot change this value |
|
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. |
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 |
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 this database. If you choose a very high value for MaxUserTasks, the database system requires a lot of 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, indicates if other applications use the database |
Changes only apply after a restart of the database |
|
RunDirectoryPath |
RUNDIRECTORY |
Run directory of the database A relative path is interpreted relatively to the independent data path. |
Changes only apply after a restart of the database |
Glossary, Run Directory |
UseMirroredLog |
LOG_MIRRORED |
Specifies whether the database system mirrors the log area This parameter is relevant only when you create a mirror volume with the Database Manager CLI. Database Studio automatically adjusts this parameter when a mirror volume is created. |
Changes only apply after a restart of the database |
Glossary, Log Mode |
Name (from version 7.7.03) |
Old Name (up to and including version 7.7.02) |
Description |
Change Restrictions |
More Information |
---|---|---|---|---|
CAT_CACHE_SUPPLY |
CAT_CACHE_SUPPLY |
Size of the task-specific catalog cache in memory which 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 will not compress the cluster. |
Can be changed in ONLINE or ADMIN operational state |
- |
ClusterCompressionThreshold |
- |
Minimum number of blocks in a cluster which is eligible for compression that needs to be reached before the database system starts compressing the cluster (in 1/1000 of the total block count) |
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 by using database tools (such as the standard_date_mask in the Loader) or 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 |
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 exported 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 |
EnableQuery |
- |
Specifies whether the system is to perform an extended semantic analysis of SQL statements |
Can be changed in ONLINE or ADMIN operational state |
- |
EnableQueryRewrite |
OPTIMIZE_QUERYREWRITE |
Prerequisite: EnableQuery must be 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 the access to the CPU for a different task of 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 |
Suppresses the formatting of data volumes when a new database is created; only used for test purposes |
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 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 Delay in seconds that the standby instance uses for data changes in the master instance. A question mark (?) is the placeholder for the three-digit identification of the standby instance. |
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 hot standby instance A question mark (?) is the placeholder for the three-digit identification of the standby instance. The default value for the master instance 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 hot standby 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 instance to synchronize the standby instances (in s) |
Changes only apply after a restart of the database |
See above |
IndexListsMergeThreshold |
OPTIM_MAX_MERGE |
Specifies the decision 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, |
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 that the SQL optimizer can use for a read operation per join step |
Can be changed in ONLINE or ADMIN operational state |
SQL Optimizer, Joins |
KernelMessageFileSize |
KERNELDIAGSIZE |
Size of the kernel log (in KB) |
Changes only apply after a restart of the database |
Database Administration, Log Files |
KernelMessageHistoryCount |
KNLMSG_HISTORY_NUM |
Number of stored old kernel logs The system moves the last kernel log to the log history directory at each database start |
Changes only apply after a restart of the database |
Database parameter DiagnoseHistoryPath |
LoadBalancingCheckLevel |
LOAD_BALANCING_CHK |
Time interval in which the database system checks whether it should use load balancing (in s) |
Changes only apply after a restart of the database |
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 stored in the working memory by the kernel 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 (defines the maximum number of log partitions) |
Changes only apply after a restart of the database |
|
MaxMemoryAllocationSize |
MEMORY_ALLOCATION_LIMIT |
Maximum amount of memory to be used by the database (in KB) |
Changes only apply after a restart of the database |
- |
MaxParallelLiveCacheTraceFiles |
_MAX_MESSAGE_FILES |
Maximum number of trace files that can be open simultaneously |
Changes only apply after a restart of the database |
- |
MaxServerTasks |
MAXSERVERTASKS |
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 initial to the computer on which the master instance of the hot standby system is located. If the master instance breaks down, then the name transfers to the standby instance, which takes on the master role. |
Changes only apply after a restart of the database |
Glossary, Hot Standby |
RequestTimeout |
REQUEST_TIMEOUT |
Maximum waiting time for a lock to be released (in s); limits waiting times for a lock to be released by another user for all database sessions. If a lock request cannot be satisfied within the time defined here, a message is sent to the waiting database session. The database system rolls back any changes previously executed within respective the transactions (ROLLBACK). |
Changes only apply after a restart of the database |
Concepts of the Database System, Locks |
RequestUpdateStatisticsThreshold |
- |
If the system detects that a table's size has changed by more than the value specified in this parameter (in percent) since the last statistics update, it will mark 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 total of all rows is divided in the lock list This division enables 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 |
Changes only apply after a restart of the database |
- |
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 total of all tables in the lock list is divided This division enables 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> |
Maximum number of pages that are available in the individual task types for each user kernel thread Each user kernel thread has its own trace area in the working memory. <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 total of all transactions in the lock list is divided This division enables parallel access to the lock list. |
Changes only apply after a restart of the database |
Glossary, Critical Section |
UpdateStatSampleAlgorithm |
UPDATESTAT_SAMPLE_ALGO |
Defines the algorithm 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 |
UseAutomaticBadIndexRecreation |
AUTO_RECREATE_BAD_INDEXES |
Indexes marked as BAD are recreated automatically after a restore. |
Changes only apply after a restart of the database |
Glossary, Index |
UseBackupSecurityDescriptor |
USE_BACKUP_SECURITY_DESCRIPTOR |
Only for Microsoft Windows Specifies whether the system uses the Microsoft Windows Security Descriptor for backups to data carriers of the file type Note If you want to backup to a Samba share, set this parameter to NO. End of the note. |
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 |
- |
UseLobClustering |
CLUSTERED_LOBS |
Specifies whether the database system stores the LOB values as clusters in the data area |
Can be changed in ONLINE or ADMIN operational state |
- |
UseSharedSQL |
SHAREDSQL |
Activates Shared SQL |
Parameter can be activated in ONLINE or ADMIN operational state but not deactivated |
Glossary, Shared SQL |
UseUnicodeColumnCompression |
- |
Specifies whether application data in columns of type (VAR)CHAR UNICODE in newly created tables is stored 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 define 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 |
Name (from version 7.7.03) |
Old Name (up to and including version 7.7.02) |
Description |
Change Restrictions |
More Information |
---|---|---|---|---|
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 |
- |
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 |
- |
EnableSymbolDemangling |
SYMBOL_DEMANGLING |
Specifies whether the database system performs C/C++ demangling |
Can be changed in ONLINE and ADMIN operational state |
- |
EnableSynchronousTaskIO |
_USE_IOPROCS_ONLY |
YES: I/O operations are executed only by special I/O threads NO: The kernel decides whether a task is to execute an I/O operation itself or delegate the I/O operation to a special I/O thread |
Can be changed in ONLINE and ADMIN operational state |
- |
EnableVariableInput EnableVariableOutput |
USEVARIABLEINPUT |
Specifies whether the current length of the variable contents or the maximum length of these variables is transmitted between client and kernel. In the latter case, the maximum length may be used depending on the data type of the variables. |
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 |
|
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 of the dump file that is written by the kernel when the system crashes To this file, the database system writes the contents of the data cache and the converter. Size your system so that sufficient memory space is available for this file (approximately CACHE_SIZE + 10%). |
Changes only apply after a restart of the database |
Parameter DIAG_HIST_NUM |
KernelTraceFile |
_KERNELTRACEFILE |
File to which the kernel writes trace entries The kernel only writes trace entries 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 load balancing Specifies which time delay should be regarded as equal when comparing waiting tasks (as a percentage) |
Changes only apply after a restart of the database |
- |
LoadBalancingWorkloadThreshold |
LOAD_BALANCING_DIF |
For load balancing Specifies by how much longer the task to be moved has to wait in its user kernel thread than the task that has been waiting the longest in the target user kernel thread (as a percentage) |
Changes only apply after a restart of the database |
- |
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 |
- |
PreservedDBAnalyzerTasks |
- |
Minimal 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 |
Minimal number of event tasks in the floating service task pool See also FloatingServiceTasks The database system uses event tasks both for Event Dispatcher 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 |
Database Manager CLI, |
MaxPagerTasks |
MAXPAGER |
Maximum number of pagers; calculated by the database system from MAXDATAVOLUMES and other parameters |
Not changeable You can override this parameter with XP_MAXPAGER. |
- |
MaxSavepointTimeInterval |
_RESTART_TIME |
Minimum time between two savepoints (in s); corresponds to the time that is required for a restart after a system crash Furthermore, 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 |
- |
MaxSpecialTaskStackSize |
MAX_SPECIALTASK_STACK |
Maximum size of the stack that is used by special tasks (all 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 |
- |
MaxTempFilesPerIndexCreation |
_IDXFILE_LIST_SIZE |
Number of temporary result files in the case of 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 |
- |
MaxVolumes |
MAXVOLUMES |
Maximum number of data and log volumes including mirrored volumes |
Changes only apply after a restart of the database |
- |
MiniDumpType |
MINI_DUMP |
Defines whether the system writes the memory dumps knlmini.dmp and srvmini.dmp (for postmortem debugging) and how much information these dumps contain |
Changes only apply after a restart of the database |
- |
OMSStreamTimeout |
OMS_STREAM_TIMEOUT |
Maximum wait time for all database sessions that may elapse until the reply to an OMS stream request to a client (in s) |
Can be changed in ONLINE and ADMIN operational state |
- |
ReadAheadLobThreshold |
_READAHEAD_BLOBS |
Number of pages from which large LOB values are imported in advance by additional server tasks 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. |
Can be changed in ONLINE and ADMIN operational state |
- |
ReservedCommandBufferReplySize |
_MINREPLY_SIZE |
Minimum size of the memory that is available in a package (shared memory segment) for the reply 0: The whole package is available for the request/reply. |
Changes only apply after a restart of the database |
- |
RTEDumpFileName |
_RTEDUMPFILE |
File 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 |
- |
ShowMaxStackUsage |
SHOW_MAX_STACK_USE |
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 |
- |
TaskCluster01 to TaskCluster03 |
_TASKCLUSTER_01 to _03 |
These parameters describe 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 |
- |
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 |
- |
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 |
- |
UseColumnCompression |
COLUMNCOMPRESSION |
Specifies whether the column values can be stored in variable length or not. Default value: YES (columns have variable length, so the values can be compressed if necessary) Only for columns that are not primary key columns |
Can be changed in ONLINE and ADMIN operational state |
- |
UseExtendedOracleSQLMode |
_SERVERDB_FOR_SAP |
Specifies whether the database is being used in an SAP system |
Can be changed in ONLINE and ADMIN operational state |
- |
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 recovery 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 |
- |
UseFilesystemCacheForVolume |
(USE_OPEN_DIRECT) Caution This parameter replaces the USE_OPEN_DIRECT parameter, but with a different logic. For backward compatibility, DeprecatedParameter29 has been introduced as a direct replacement for USE_OPEN_DIRECT, see Obsolete Database Parameters. After migrating from an earlier database version and if USE_OPEN_DIRECT was set explicitly for example using a script, the system changes UseFilesystemCacheForVolume to the opposite value. Note though that after you have changed UseFilesystemCacheForVolume for the first time, it does not depend on USE_OPEN_DIRECT any longer. End of the caution. |
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 |
- |
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 |
- |
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 |
- |
UseSystemTriggers |
ENABLE_SYSTEM_TRIGGERS |
Specifies whether system triggers are called when the database is restarted |
Changes only apply after a restart of the database |
- |
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 |
- |
Name (from version 7.7.03) |
Old Name (up to and including version 7.7.02) |
Description |
Change Restrictions |
More Information |
---|---|---|---|---|
MinRetentionTime MaxRetentionTime |
MIN_RETENTION_TIME MAX_RETENTION_TIME |
Specifies (in min) when 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 |
OmsHeapThreshold |
OMS_HEAP_THRESHOLD |
Specifies memory usage by the OMS heap (in %) |
Changes only apply after a restart of the database |
- |
OmsMaxHeapSize |
OMS_HEAP_LIMIT |
Specifies the maximum size of the OMS heap (in KB) |
Changes only apply after a restart of the database |
- |
OmsSubHeaps |
OMS_HEAP_COUNT |
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 |
Specifies memory usage by the OMS heap (in KB) |
Changes only apply after a restart of the database |
- |