Manage the maximum memory allocation in SAP HANA Systems

[Former Member]

Hello,

I´m with some doubts regarding one thing about the management of each HANA instances. At this moment I have one appliance server that has 130Gb of RAM and it has one SAP Hana system (instance) installed (SID Hana: HL1) but today I want to install in the same appliance another SAP Hana system (other instance) called HL2! But my goal is to split the RAM memory between these two Hana systems (HL1 and HL2). During the installation of HL1 I didn´t restrict the maximum memory allocation value and I think I should had done this restriction right here at this stage, but I didn´t...

I´m talking about this following screen during the installation of SAP Hana system (HL1):

So now, as I said before, I want to install another SAP Hana system (HL2) in the same server/appliance but before doing that I want to know how can I manage the maximum memory allocation that is set to the HL1 instance and if it´s possible to decrease the allocated memory to 75Gb RAM! How can I do that? Is there any parameter that is set to the HL1 instance...!? Can you help me please?

Thank you,

samid raif

[Former Member]

Hi Armenio,

On HL1 change the parmater global_allocation_limit parmater to 75 GB. In this way you can restrict the HL1 to use 75 GB of memory.

Regards,

Pavan Gunda

[michael_devine]

Hi,

Im not sure about the decrease but could the global allocation limit parameter help here?

https://cookbook.experiencesaphana.com/bw/operating-bw-on-hana/hana-database-administration/system-c...SAP BW on HANA Cookbook

Regards,

Michael

[Former Member]

Hello Michael,

I´m not sure if that's what I'm asking for because in point 6.26 max_mem of the guide "SAP HANA Server Installation and Update Guide" it is mentioned some tips but I don´t not exactly how can I done that... isn´t very well explained unfortunately!

Can you tell me something about this max_mem and restrict_max_mem parameters?! You have more information about this?

Because when I try to search that parameter (max_mem) in SAP Hana Studio I see the following value is 200, but I don´t know exactly what this means because as I mentioned previous, I set 130Gb RAM for this sap hana system (HL1)!

Can you help me please?

Any tips?

Kind regards,

samid raif

[Former Member]

Hi Armenio,

How have you overcome this?

I am in a similar situation wherein, I have got to install two instance in the same box and I need to be careful on this memory limit.

[Former Member]

See SAP Note 1999997 and use the global_allocation_limit parameter to restrict the maximum amount of memory usable by a SAP HANA instance.

[Former Member]

Hi Martin,

This is one such parameter to be used after the instance is built. So, assume, I have 1TB memory, then for the two instances to be built on the same box, while installing the DB, under the "define system properties" tab,  I will give 500GB each by pulling the slider to the left?

[Former Member]

I am not familiar with the installation details, but probably that's what you can do. Alternatively you can manually set the parameter after the installation. In any case you should make sure that around 30 GB of memory is available for the operating system and external tools, so set the allocation limits to slightly less than 50 % of the available physical memory.