Database Parameters SAP LiveCache Versions 7.5, 7.6 and 7.7

SAP Note

Header Data

Symptom

This note provides recommendations for setting the database parameters for SAP liveCache systems with Version 7.5, 7.6, or 7.7. If you are using the SAP liveCache Version 7.9, use SAP Note 1567117.

Other Terms

OMS_HEAP_COUNT, OMS_HEAP_LIMIT, MAXCPU, LOAD_BALANCING_CHK, LOG_IO_QUEUE, MP_RGN_LOOP, LOG_QUEUE_COUNT, SHAREDSQL, MAXLOCKS, MaxCPUs, OmsMaxHeapSize, OmsSubHeaps, LoadBalancingCheckLevel, MaxExclusiveLockCollisionLoops, LogQueueSize,LogQueues,MaxSQLLocks, UseSharedSQL, InitialAllocatorSize

Reason and Prerequisites

When a new SAP liveCache version is delivered, the recommended value of a database parameter has changed or a new parameter has been imported that must be set explicitly. For the release of a certain SAP liveCache version, see the Product Availability Matrix (PAM). This SAP Note does not apply to SAP liveCache Version 7.9. If you are using the SAP liveCache Version 7.9, use SAP Note 1567117.

Solution

You can use the most recent version of the configuration file of the Database Analyzer (SAP Note 1111426) to check the correct setting of the database parameters. If you use the Database Studio or the liveCache Assistant (transaction LC10) for parameter changes, we recommend that you enter the reason for the database parameter change (for example, enter the SAP Note number, customer message number, or the PTS number) in the comment field. You generally set the database parameters described here to a value other than the value of the default setting only if errors or problems can be avoided if you do so. Use the SAP liveCache version and the operating system in use to determine the parameter values required for your SAP liveCache from the following list. Also refer to the specified notes, which contain further information. The parameter names were changed with SAP liveCache Version 7.7.03. You can continue to use the old name of a database parameter and this name continues to be stored in the file cserv.pcf under DEPRECATEDID. In each case, the new parameter name is specified after the name that was previously used and is in brackets. There is a list of the old and new database parameter names in the SAP MaxDB documentation under the glossary entry "Database Parameter" (for example, at http://help.sap.com/saphelp_nw73/helpdata/en/44/bd1ec6a5d51388e10000000a155369/frameset.htm).

1. _LOCKMANAGER_ENABLED (only SAP liveCache Version 7.6)

The database parameter _LOCKMANAGER_ENABLED was introduced as of SAP liveCache Version 7.6.04.

If you set this parameter, an optimized implementation of the LockManager is activated that is responsible for the management of object locks. In some systems, this results in improved performance in high load situations because collisions are avoided on "kb511:ConsistViewRWLock_1" (==> many tasks have the status "VenterRWregion").

Recommended:

NO: for SAP liveCache version < 7.6.05 patch level 12 (PTS 1154591 + 1156927) YES: for SAP liveCache version >= 7.6.05 patch level 12

As of SAP liveCache Version 7. 7, this optimization is always active. Therefore, the database parameter is no longer required as of this version and has been removed.

2. INIT_ALLOCATORSIZE (InitialAllocatorSize) (SAP liveCache version 7.7 only)

You can use this database parameter to define the initial size of the memory area that is allocated when a database session is set up (connect). Experience has shown that the default value is not always optimal and that, depending on the application profile, more memory allocations and releases can occur. A value that is too small can have a negative effect on performance.

Recommended:

Value >= 1024000

See Note 1517013.

3. IOTicketQueueSynchronisationMode (only AIX)

See SAP Note 1698867 for the correct settings for this database parameter.

4. LOAD_BALANCING_CHK (LoadBalancingCheckLevel 7.7.03 to 7.7.07.05, LoadBalancingCheckInterval as of 7.7.07.06)

With the help of load balancing, user tasks can change the UKT (user kernel thread). This allows SAP liveCache to optimize the use of the processors that are available to SAP liveCache in accordance with the MaxCPUs database parameter.

833216 - Database parameters SAP liveCache versions 7.5, 7.6 and 7.7

Version 41 Validity: 02.11.2012 - active Language English

Released On 02.11.2012 09:00:47

Release Status Released for Customer

Component BC-DB-LVC liveCache

BC-DB-LCA liveCache Applications

Priority Recommendations / Additional Info

Category Help for error analysis

Other Components

See Note 695721.

Recommended:

0: always with Microsoft Windows 32-bit 0: SAP liveCache version < 7.7.07 patch level 00 (Microsoft Windows 64-bit) 0: SAP liveCache version < 7.7.00 patch level 18 (all platforms) 0: SAP liveCache version < 7.5.00 patch level 18 (all platforms)

15: 7.5.00 patch level 18 <= SAP liveCache version < 7.5.00 patch level 35 15: SAP liveCache version < 7.6.00 patch level 30 (only Unix)

4: SAP liveCache version >= 7.5.00 patch level 35 (only Unix) 4: SAP liveCache version >= 7.6.00 patch level 30 (only Unix) 4: SAP liveCache version >= 7.7.00 patch level 18 (only Unix) 4: SAP liveCache version >= 7.7.07 patch level 00 (Unix, Microsoft Windows 64-bit)

Caution: Before an upgrade of an SAP liveCache version 7.5.00 >= patch level 35 to a Version 7.6.00 < patch level 30, you must set the LOAD_BALANCING_CHK database parameter back to a value >= 15 (also see SAP Note 832561).

Note the following: On Microsoft Windows 64-bit, you can set the database parameter only using the tool Database Manager CLI (DBMCLI), not using Database Manager GUI (DBMGUI) or Database Studio.

Remark: If you operate the SAP liveCache in a special configuration in which each user task runs in its own UKT (SAP Note 425051 or MAXCPU=MAXUSERTASKS), there is no point in activating load balancing (in this case, set the value to 0).

5. LOG_IO_QUEUE (LogQueueSize)

This sets the size of the main memory area where log entries are buffered before they are written to the log volumes. Unit: 8 KB pages

Recommended: 2000

Note that this value refers to each maximum possible number of log queues (generally this is MaxCPUs). Therefore, the main memory that is allocated when you start SAP liveCache and the area that is reserved in the log area is as follows:

MAX_LOG_QUEUE_COUNT (MaxLogQueues) * LOG_IO_QUEUE (LogQueueSize)

6. LOG_QUEUE_COUNT (LogQueues)

As of SAP liveCache version 7.6. 00, you can configure several log queues, which significantly reduces collisions to LOGQUE* regions in multiprocessor machines (MAXCPU > 1). For more information about this, also refer to SAP Note 817887.

To achieve a minimum of collisions, the number of log queues should be the same as the value of MAXCPU (MaxCPUs), which is the default setting for new installations.

Recommended:

MAXCPU (SAP liveCache version < 7.6.04) MAXCPU (SAP liveCache version < 7.7.03) 0 (SAP liveCache version >= 7.6.04) 0 (SAP liveCache version >= 7.7.03)

Important:

In SAP liveCache version 7.6 < patch level 04 or version 7.7 < patch level 03 , the database parameter LOG_QUEUE_COUNT is not adjusted automatically if MAXCPU is changed (PTS 1147929 or 1143833).

7. MAXCPU (MaxCPUs)

Maximum number of processors that SAP liveCache uses to process application orders (SQL, LCA routines).

Recommendation for dedicated SAP liveCache servers: MAXCPU = Number of SAP liveCache server processors (SAP Note 410002).

If more applications run on the SAP liveCache server (APO/SCM, DB), then you must limit MAXCPU to the largest number of processors that SAP liveCache uses, using a detailed sizing if possible. If the available sizing information is insufficient, we recommend that you set MAXCPU as follows: MAXCPU = (liveCache server processors)*2/3.

If blocks occur due to LCA routines that run a long time, you must change the SAP liveCache configuration and therefore, MAXCPU in accordance with SAP Note 425051 on Windows.

For UNIX systems, you must activate load balancing in accordance with SAP Note 695721.

For information about setting MAXCPU in virtualized environments, see Note 1459538.

Note the following:

If your system has multi-core processors, the term "Processors" refers in this context to the number of cores available in the system.

8. MAXLOCKS (MaxSQLLocks)

This sets the maximum number of SQL locks.

Recommended value: 200000

SAP Note 337773 describes potential effects if the database parameter setting is too small.

The database parameter is calculated automatically. It is only necessary to change this parameter if the calculated value is smaller then the recommended value.

9. MAXUSERTASKS (MaxUserTasks)

Maximum number of SAP liveCache connections

Remark: Each user task requires approximately 1.5 MB of memory.

Minimum for SAP liveCache version 7.5: (Number of SCM work processes)*2 + 4. See Note 205220.

Minimum as of SAP liveCache version 7.6: (Number of SCM work processes)*3 + 4

10. MP_RGN_LOOP (MaxExclusiveLockCollisionLoops or XP_MP_RGN_LOOP in SAP liveCache version 7.5)

Maximum number of attempts to access a region that has already been blocked by another task before the task is entered in a queue (until the region is accessible).

As of SAP liveCache version 7. 6, you can change the database parameter MP_RGN_LOOP directly; in Version 7.5, you must change the database parameter XP_MP_RGN_LOOP. If you set the relevant database parameter to the default value (-1 or 0), SAP liveCache will automatically calculate the actual value.

Recommended:

10000: if MAXCPU > 4 -1: in SAP liveCache versions 7.6 and 7.7, if MAXCPU <= 4 0: in SAP liveCache version 7.5, if MAXCPU <= 4

11. OMS_HEAP_COUNT (OmsSubHeaps)

Segmentation of the SAP liveCache heap for increasing parallel processing in multi-processor environments

Unit: Number of segments (minimum 1, maximum 128)

Recommended: <MAXCPU>

12. OMS_HEAP_LIMIT (OmsMaxHeapSize)

This is the upper limit up to which the OMS heap is allowed to grow.

The value to be set depends on the hardware requirements and the application profile, and it results from the sizing of SAP liveCache. The value should always be greater than zero. If you set the value to zero, the limitation is removed. This may lead to an uncontrolled memory consumption by the SAP liveCache process. In extreme cases, this may lead to an increased number of paging activities at operating system level with a relevant deterioration in performance.

Recommended: > 0

13. OPTIMIZE_OPERATOR_JOIN_COSTFUNC (only SAP liveCache version 7.6)

This database parameter influences the processing of JOIN statements.

An unfavorable setting of the database parameter may result in longer runtimes for a command that is executed by the Database Analyzer.

See Note 1422648.

Recommendation as of SAP liveCache version 7.6.05: NO

14. SHAREDSQL (UseSharedSQL)

The caching of SQL statements in pure SAP liveCache environments has not brought any clear advantages so far. In contrast, disadvantages due to collisions in RW regions (for example, CommandCache:CommandLock) were observed especially on larger systems.

Recommended: NO

You can change the database parameter value for the current database session for database parameters with the CHANGE=RUNNING attribute. Changes to the values for database parameters with the attribute CHANGE=OFFLINE only become valid when the database is restarted. For example: dbmcli> param_getfull SHAREDSQL ... CHANGERUNNING ... dbmcli> param_put -running -permanent SHAREDSQL <value> OK You can also use the DBM command param_getfull to check the current value of the database parameter. This is displayed in the row 'ACTIVEVALUE'.

Validity

This document is not restricted to a software component or software component version

References

This document refers to:

SAP Notes

1014605 SAP liveCache 5.1 LCA Build 02








1055038 SAP liveCache 6.0 LCA build 05




1083639 liveCache 7.7 Installation






1111426 Datenbank parameter check for SAP MaxDB/liveCache





1139904 FAQ: SAP MaxDB/liveCache database parameters


1147936 Parameter recommendations for OneDB systems




























1422648 DBAnalyzer liveCache 7.6.as of SP 05: Slow data collection


1459538 Configuration of MaxCPUs in virtual environments





1517013 Loss of performance due to frequent memory allocations




1567117 Parameter values for liveCache Version 7.9








1698867 SAP MaxDB/liveCache crash on AIX/SUN: RTECont_LockFreeFIFO

496318 Parameter values as of liveCache Version 7.4.02

686013 Additional information about upgrading to liveCache 7.5.0

713381 Importing SAP liveCache Version 7.5.00 for SAP SCM 4.1

719652 Setting initial parameters for liveCache 7.5, 7.6, 7.7

817887 High collision rate in LOGQUEUE region

832561 Additional information about the upgrade to liveCache 7.6


866331 SAP liveCache 5.0 LCA-Build 02



This document is referenced by:

SAP Notes (69)


936058 FAQ: SAP MaxDB Runtime Environment





496318 Parameter values as of liveCache Version 7.4.02

1567117 Parameter values for liveCache Version 7.9

936058 FAQ: SAP MaxDB Runtime Environment

1698867 SAP MaxDB/liveCache crash on AIX/SUN: RTECont_LockFreeFIFO


1139904 FAQ: SAP MaxDB/liveCache database parameters

817887 High collision rate in LOGQUEUE region



1459538 Configuration of MaxCPUs in virtual environments



713381 Importing SAP liveCache Version 7.5.00 for SAP SCM 4.1


1147936 Parameter recommendations for OneDB systems


686013 Additional information about upgrading to liveCache 7.5.0








1517013 Loss of performance due to frequent memory allocations











832561 Additional information about the upgrade to liveCache 7.6

719652 Setting initial parameters for liveCache 7.5, 7.6, 7.7






























1422648 DBAnalyzer liveCache 7.6.as of SP 05: Slow data collection

1111426 Datenbank parameter check for SAP MaxDB/liveCache


Database Parameters SAP LiveCache Versions 7.5, 7.6 and 7.7

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