Maxdb Memory Tunning

[Former Member]

I´m planning a SAP installation on a host that already has a SAP instance (Maxdb/Sun) , currently the memory on this host is not well tunned , since the host has 16gb and only 4gb are available, and the only sap product running is ECC 6.0 Unicode. So is there any guide on Maxdb and Sap for tunning the memory?

Thank you.

[Former Member · Accepted solution]

Thank you for the information !!

Since we have already installed the system DEV with 64 bits the sapnote you mention is not relevant for us, but could be usefull for others.

What it is usefull was the rule of the thumb regarding the cache_size , didnt know that one.

I will check the database analyzer and I found that there is a resource monitor called xcons accesible from db50. Have to check both.

If I undestand right all memory managment for Maxdb is by allocating the correct cache_size or are there any other parameters?

I have follow all notes regarding maxdb parameters for the first intance DEV. So those parameters have been set. Maybe I should consult SAP directly?

Maybe its a SAP memory managment issue instead of a MAXDB issue that the DEV instance is taking 12gb ram with almost no activity on it.

Anyway thanks for your help, if you find any more notes regarding Memory Managment for SAP and Maxdb , please let me know , I will check them.

[Former Member · Accepted solution]

Hello Daniel,

the cache_Size ( use transaction DB50 to check the Cache Size) is the main part of the memory the database is using,but there are a lot of small parts of memory which are used as well. The size depends on the number of MAXUSERTASKS, number of backup devices; number of volumes configured etc. If you want to know the storage used by the database you can use x_cons <DBNAME> show storage.

You will find information about the memory which is used by the database after the restart in the knldiag file in RUNDIRECTORY. You can also use the systemtable 'allocatorstatistic' (using SQLStudio) to get the current memory size the database is using.

I don't think that the database is configured with nearly 16 Gbyte memory, everything sounds like the SAP Memoery management is allocating this memory.

I don't know much about SAP memory management but you should check the SAP profiles and check the Buffer sizes and extended memory.

You can use transaction ST02 to check how many memory is used by the SAP System instance.

Hope this will help you a little bit. Otherwise it would be great to contact my SAP colleagues with an customer call.

Regards, Christiane

MaxDB/liveCache Development Support

SAP AG

[Former Member]

Os : SPARC Sun 10 with Zone Resources

DB : Maxdb 7.6.01.15

SAP : ECC 6.0

UNICODE : YES

Architecture : 64 bits

Memory : 16gb

Currently : 1 SAP Instance ECC 6.0 DEV 4gb free memory

Planning : a second SAP Instance ECC 6.0 QAS need memory optimization.

I search those tunning you mention but coudn't find any that reference to memory managment , all where for sql optimization or database cachet hit ratio , and so on , couldn't find any regard how to optimize the system memory.

Thank you.

[Former Member]

Hello Daniel,

I just added some information about memory in this section.

But to get information about if your system has enough memory yet use DB-Analyzer for the installed system to check the DATA CACHE HITRATE .

The sizing of the new system depends on the size of the database , the number of transactions and the kind of transactions , the number of users etc. I don't think that you can get exact information without a detailed analysis of the old and the new system.

This can be done by the SAP colleagues when you open a customer call and ask for remote consulting.

Regards, Christiane

Regards, Christiane

[Former Member]

Hello Daniel,

do you use 32bit or 64-bit? There are only 4 Gbyte Memory available?

You have to check how many memory does the ECC system use. Database Caches R/3 Memory etc.

You will find more information about this in MAXDB SDN Wiki -> <a href="https://wiki.sdn.sap.com/wiki/x/jRI">MaxDB Tuning</a>

There are sections about Parameter configuration and transactions which can be used to analyze the system.

There are a lot of SAP FAQ Notes which tells about MaxDB tuning. Search in the SAP Customer system for Notes on component Bc-DB-SDB and FAQ

Hope this will help to start analysis.

Regards, Christiane