First Steps - SAP MaxDB Problem Analysis
This page provides information about the first steps in a problem analysis related to SAP MaxDB.
If the SAP MaxDB is suspected to be the cause of a problem with the SAP system, the first place to look for more information is the Database Assistant/DBA Cockpit (DB50/DBACOCKPIT transaction).
As this page just lists some first-steps in error analysis make sure to check the SAP MaxDB Support Guide for a more detailed troubleshooting guideline.
Table of contents
What needs to be checked always?
Although database problems can have very different causes there are some information that are needed in any case.
The following questions need to be answered:
What exactly is the problem?
How can the issue be observed? Where? All servers/users/transactions?
Try to describe the problem as specific as possible.
Write down the facts you know.
If necessary draw a picture of the problem setup.
What database version is used? On what hardware? What is the parameter setup?
Where to check
Check KnlMsg/KNLDIAG file!
In the startup part of the KnlMsg file all these information can be found.
Look for information that look similar to this example:
SAP MaxDB software/platform information (example)
Are there any error messages?
Where to check
Check KnlMsg/KnlMsgArchive.err files.
Check if there are saved KnlMsg files in DIAGHISTORY folder.
Also check the SAP NetWeaver log files via SAP transactions like SM21, ST22, ST11, etc.
Is the software correctly installed?
Some errors result from incorrectly installed software, so make sure that the database software has been correctly installed and that it wasn't changed afterwards.
Where to check
run sdbverify as root/administrator!
SDBVERIFY can also be used to check client software installations on application servers!
There should be no missing or modified files and no files with changed permissions.
SDBVERIFY output (example)
After the general information have been gathered, many critical issues fall in one of the following problem categories:
- Performance problems
- Database 'halts'
- Connection problems
The following sections provide some hints what to check for each kind of problems.
Are the parameters setup correctly as recommended by SAP?
You always use the Database Analyzer Check to check your current SAP MaxDB Kernel parameter setting.
Detailed Information can be found in SAP MaxDB Database Parameter Recommendations.
To review and change the current parameter settings you can use the Database Studio, Database Manager CLI (DBMCLI: DBM command param_directgetall) or the Database Assistant/DBA Cockpit (Transactions in CCMS, DBACOCKPIT: Administration – Parameters. Choose Expert View in the Goto menu to get a list of all parameters at once).
Statistics that fit well to the current data set are vital for the SAP MaxDB optimizer to find the optimal data access strategies.
Therefore make sure that the statistics are up to date and that the sample size is correctly set. This can easily be done with the report ZZ_SET_SAMPLE_SIZES from SAP note 808060 Changing UPDATE STATISTICS sample values