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This note contains frequently asked questions (FAQs) about MaxDB kernel parameters. It provides answers and refers you to other information sources.
The note is by no means complete.
1. What are MaxDB kernel parameters?2. Which tool can I use to display and change MaxDB kernel parameters?3. Where does the system store MaxDB kernel parameters?4. Is there a history for the kernel parameter file?5. How can I activate an old version of a kernel parameter file?6. How can I read the parameter file from a backup?7. Is there a history that logs the changes to individual parameters?8. What types of kernel parameters exist?9. How can I display the properties of kernel parameters?10. What do the individual properties of the parameters mean?11. Can I change kernel parameters while the database is running? When do these parameter changes become active?12. Where can I find information about which calculation formulas have been defined for individual parameters?13. How do I ensure that dependent parameters are recalculated after a parameter change?14. Where can I find information about parameter recommendations?15. Where can I find information about parameter recommendations for ONE DB or BusinessByDesign systems with MaxDB?16. If I have changed parameters due to an error in the software, does the database report whether a change can be reset?17. Where can I find more information about MaxDB kernel parameters?18. Where can I find more detailed information about MaxDB kernel parameters that affect the optimizer?19. As of MaxDB Version 7.7.03, new names were assigned to the kernel parameters. Where can I find a list that contains both the old and the new parameter names in comparison?20. What is the importance of the parameter TIME_MEASUREMENT?21. Where can I find information about parameters which can be used to alter MaxDB Task Scheduling?
Other terms
FAQ, frequently asked questions, MaxDB/liveCache, parameter, cserv.pcf
Reason and Prerequisites
You use a MaxDB database in the OLTP environment, the BI environment, the Content Server environment, or the liveCache environment.
The MaxDB/liveCache database version you use is Version 7.6 or higher.
You can find an overview of all the available MaxDB FAQ notes in the SAP Developer Network (SDN) at:
https://wiki.sdn.sap.com/wiki/x/GkM
Solution
1. What are MaxDB kernel parameters?
MaxDB kernel parameters are used to configure a MaxDB/liveCache database.2. Which tool can I use to display and change MaxDB kernel parameters?
You can use the database tools DBMGUI, DBMCLI, or the Database Studio to configure, display, and change the kernel parameters.
In the SAP environment, you can use transaction DB50 or LC10 to display and change kernel parameters.

More information about displaying and changing the parameters is available in the MaxDB documentation:
MaxDB Version 7.6:
http://maxdb.sap.com/doc/7_6/bd/5a028564adcb43b4259580bca22a7e/frameset.htm
MaxDB Version 7.7:
http://maxdb.sap.com/doc/7_7/44/bd1ec6a5d51388e10000000a155369/frameset.htm
3. Where does the system store MaxDB kernel parameters?
The system stores the kernel parameters in a parameter file. The system stores this parameter file in the file system in binary format in the directory <INDEPDATA>/config. The name of the parameter file corresponds to the database name. You can only retrieve the parameter file with a database tool (DBMCLI or DBMGUI).
When you carry out backups of the type SAVE DATA or SAVE PAGES, the system writes the content of the parameter file to the backup media.4. Is there a history for the kernel parameter file?
Yes. When you make parameter changes, the system copies the old parameter file to
<INDEPDATA>/config/<instance>.<number>. The system stores a maximum of 10 versions of the parameter file.
After you add a new volume, the system deletes all the versions of the parameter file that are not current because these have then become unusable for the current configuration.
To display the parameter history, use the dbmcli command ‘param_gethistory’.5. How can I activate an old version of a kernel parameter file?
Use the dbmcli command ‘param_restore’ and specify the required version to activate an older version of a parameter file. For example, this is useful if a parameter file was destroyed due to a ‘Filesystem Full’.
Note the following: Before you execute this command, you must first back up the current parameter file.6. How can I read the parameter file from a backup?
You can use the DBMCLI command ‘recover_config’ to read the parameter file from the backup.7. Is there a history that logs the changes to individual parameters?
You can use DBMCLI ‘param_gethistory’ to display the changes to all parameters, or you can use ‘param_gethistory <parameter name>’ to display the changes to individual parameters.
In SAP systems, you can display the changes to parameters using transaction DB50 or LC10. Here, you can trace changes to parameters back to the creation of the database. The history is not restricted to 10 versions.8. What types of kernel parameters exist?
Kernel parameters are divided into three classes:
General:
These parameters are set by database administrators.
Extended:
These parameters are set in consultation with MaxDB Support or by implementing notes from the database administrator.
Support:
These parameters are set by MaxDB Support or the developers.
Note the following:
If you change extended parameters or support parameters, specify the note number or the customer message number in the comment field so that you can reproduce why a parameter was changed.
param_put [-running] [-permanent] <keyname> <value> [<comment>]
If the comment contains blank characters, set the comment in double quotes.9. How can I display the properties of kernel parameters?
The properties of kernel parameters determine, for example:
- whether you can change a parameter while the system is running, and whether the change is immediately active as a result,
- whether you must assign a value to the parameter,
- whether a parameter has dependencies on other parameters,
and so on.
You can use the dbmcli command ‘param_getfull <parameter name>’ to display the properties of a parameter.10. What do the individual properties of the parameters mean?
The most important properties of the parameters are as follows:
CHANGE:
If the property CHANGE has the value RUNNING, you can change the parameter while the system is running. The value OFFLINE means that the parameter change becomes active only after you restart the database offline.
INTERN:
The value of this parameter is not contained in the parameter file (YES).
MANDATORY:
The parameter value must be assigned (YES | NO)
CLEAR:
During a database copy, the parameter is not copied (YES | NO)
DYNAMIC:
Automatic numbering (for example, DATAVOL_?) YES | NO
OVERRIDE:
The parameter value may be changed YES | NO | HIGHER
MODIFY:
The parameter may be changed after generation of the instance. YES | NO
CLASS:
Classification General, Extended, …
DEPRECATEDID:
The parameter has an alias name that is not displayed in the MaxDB tools. After you change from a version lower than Version 7.7.03 to Version 7.7.03 or higher, the old parameter name is recorded here.
VALUESET:
Permitted values <values>
MAX:
Maximum parameter value (numeric) <value>
MIN:
Minimum parameter value (numeric) <value>
11. Can I change kernel parameters while the database is running? When do these parameter changes become active?
If parameters have the property CHANGE RUNNING, you can change these parameters online (while the system is running), and they also become active without restarting the database.
If parameters have the property CHANGE OFFLINE, the changes to these parameters become active only after a db_offline.
12. Where can I find information about which calculation formulas have been defined for individual parameters?
Calculation formulas for parameters are stored in the file cserv.pcf in the directory [INSTROOT]/env. Do not change the file cserv.pcf under any circumstances unless instructed to do so by MaxDB Support or MaxDB Development.13. How do I ensure that dependent parameters are recalculated after a parameter change?
You can use the DBMCLI command param_checkall to ensure that the parameters are consistent with each other. When you make parameter changes using DBMGUI or the Database Studio, this param_checkall is executed implicitly.14. Where can I find information about parameter recommendations?
Initial parameter recommendations that differ from the default are available in the following notes:
MaxDB Version 7.5:
Note 767635 parameter recommendation
In addition, for BW systems, Note: 901377.
Note 817934 parameters that can be changed online
MaxDB Version 7.6:
Note 814704 parameter recommendation
In addition, for BW systems, Note: 901377.

MaxDB Version 7.7:
Note 1004886 parameter recommendation
liveCache:
Note 719652 Setting initial parameters for liveCache 7.5 or 7.6
Note 817884 Parameter values as of liveCache Version 7.5.00
Note 833216 Parameter values as of liveCache versions 7.6 and 7.7
These parameter notes do not contain all the kernel parameters because we cannot provide general recommendations for all parameters. Parameters (for example, CACHE_SIZE) that depend on the installation, the hardware configuration, and so on, cannot be listed in these notes.15. Where can I find information about parameter recommendations for ONE DB or BusinessByDesign systems with MaxDB?
See Note 1147936
16. If I have changed parameters due to an error in the software, does the database report whether a change can be reset?
The Database (DB) Analyzer can check parameter settings that differ from the recommendations. For more information, see Note 1111426.
17. Where can I find more information about MaxDB kernel parameters?
More information about the kernel parameters is available in the MaxDB documentation:
MaxDB Version 7.6:
http://maxdb.sap.com/doc/7_6/24/037f409cd50a1ae10000000a155106/frameset.htm
MaxDB Version 7.7:
http://maxdb.sap.com/doc/7_7/44/bd1ec6a5d51388e10000000a155369/frameset.htm
The MaxDB Internals Workshop WB550 also contains a chapter about the MaxDB kernel parameters. At maxdb.sap.com
you have access to the documents for the chapter Parameter Version 7.6:
http://maxdb.sap.com/training/internals_7.6/kernel_parameters_EN_76.pdf
18. Where can I find more detailed information about MaxDB kernel parameters that affect the optimizer?
The SAP Developer Network (SDN) provides extensive information about the parameters that affect the optimizer. Use the following link:
https://wiki.sdn.sap.com/wiki/x/Fd19. As of MaxDB Version 7.7.03, new names were assigned to the kernel parameters. Where can I find a list that contains both the old and the new parameter names in comparison?
The MaxDB documentation also provides a list that contains both the old and the new parameter names in comparison.
http://maxdb.sap.com/doc/7_7/44/bd1ec6a5d51388e10000000a155369/frameset.htm20. What is the importance of the parameter TIME_MEASUREMENT?
You can use this parameter to activate the time measurement in Version 7.6. Information for MaxDB Version 7.6 is available in the parameter Note 814704.
In MaxDB Version 7.7, there is currently no parameter that corresponds to parameter TIME_MEASUREMENT. PTS: 1153399.21. Where can I find information about parameters which can be used to alter MaxDB Task Scheduling?
See expert Note 1153461: Altering MaxDB Task Scheduling.