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HANA Memory allocation

chris_clarke
Explorer
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Hi all,

I have a question regarding the global allocation limit setting within HANA.  I understand that by default this is set to 0 and as a result HANA uses what memory it requires up to around 90% of available memory.  My question is what is the behaviour when you actually set this to a value?  I'll illustrate with an example.

I have a server with 200GB of memory.  With one instance, HANA will use up to 180GB of the memory.  If I want to install 2 instances on this server and have them use half the memory each, would I set the global allocation limit to 100 on each server, or 90 on each server? i.e. does HANA use 90% of the configured value, or the entirety of the configured value and it's left to the administrator to ensure there is enough memory for the system?

Thanks for your help

Chris Clarke

Accepted Solutions (1)

Accepted Solutions (1)

Former Member
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Hi Chris,

I think that you may configure 95GB for each instance for your example, because the two instances are existing one OS server,

based on hana memory limit concept, it can use 90% physical memory.

hope this can help you

Regards,

Jerry

chris_clarke
Explorer
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Hi Jerry,

Thanks for your response.

So I'm assuming that if I were to set each at 100GB then I could exhaust memory.  I should leave 10% free for the OS when I make these calculations and not assume that if I want 2 instances that I divide the memory in two - instead I should divide 90% of the memory in two and use those figures.

Chris

Former Member
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Hi Chris,

How about your license memory size? if you can use 128GB for HANA, then you can allocate limit 64*1024 for each instance, must not set 90% of physical memory.

It is setting base on your allow memory size of your lHANA licence.

If you can use 200GB, then you can allocate all memory except OS or other software used part.

Hope this can help you.

Regards,

Jerry

Answers (3)

Answers (3)

chris_clarke
Explorer
0 Kudos

From the replies I've had and some further research it looks like if you start setting the global allocation limit manually then you have to take into account leaving 10% of memory available for the system to use, so to use my example, 200GB split in 2 would need 90GB setting as the global allocation limit on each instance to leave 20GB free for the system.

AtulKumarJain
Active Contributor
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Hi Chris,

Please go through below link it will help you.

https://cookbook.experiencesaphana.com/bw/operating-bw-on-hana/hana-database-administration/monitori...

Best Regards,

Atul

EdinaldoJr
Product and Topic Expert
Product and Topic Expert
0 Kudos

Hi Clarke.

When you set the value to 0, the system work with 90 % physical memory, if you add more instance in this HANA BOX you can choose the memory allocation for this...it can be 50 % - %) % ( considering only 90 % of total physycal memory will be used).

This setup is done by HANA Onsite Config.. Tool  and you cna inform for example 50 % to instance 1 and 50 % to instance 2 ( Remember this value will be calculated under 90 % physical moemory).

Regards,

Edinaldo Jr