Question Re: HANA Memory after STartup in Technology Q&A

HANA Memory after STartup

Mithran — Wed, 02 Nov 2022 19:47:34 GMT

Dear Guru's,

Request you to kindly help in understanding my query.

HANA Used Memory is less and Database Resident Memory is huge. I could understand that Database Resident is something which HANA reserves, but why when the used memory is 40 GB . Peak Used is 50 GB, Which caused Database resident to reach 137 GB. Below are our server specifications and no global allocation limit is set in the server.

RAM - 188 GB

Used/Peak Used -> 40/51 GB

Database resident / Total resident -> 137/145 GB

How to measure or how to calculate which led to reserve more memory in resident. how to check how much data does HANA load whenever a restart happens like any fixed Value 40 or 50 GB.

How much Memory does HANA have it in its pool.

Thanks & Regards,

Mithran

Re: HANA Memory after STartup

mamartins — Thu, 03 Nov 2022 12:06:42 GMT

Please check the Administration Guide: https://help.sap.com/docs/SAP_HANA_PLATFORM/6b94445c94ae495c83a19646e7c3fd56/bdf26308bb571014b7bcd3bcd586aecd.html?version=2.0.03

Re: HANA Memory after STartup

Mithran — Sun, 06 Nov 2022 18:30:30 GMT

Hi m14927,
Thanks for the guide. I have a query is it possible to find out the cause why database resident memory reserves more than 50 % or 100 % of the Used Memory

THanks & Regards,
Mithran

Re: HANA Memory after STartup

mamartins — Mon, 07 Nov 2022 10:03:09 GMT

From the SAP official documentation: https://help.sap.com/docs/SAP_HANA_PLATFORM/6b94445c94ae495c83a19646e7c3fd56/bd43f1c0bb571014bf5acf22f379fd3d.html

Example:
A single-host system has 100-GB physical memory. 
Both the global allocation limit and the individual service allocation limits are 92.5% (default values). 
Therefore:

    Collectively, all services of the SAP HANA database can use a maximum of 92.5 GB.
    Individually, each service can use a maximum of 92.5 GB.

Therefore, if 2 services are running and the current memory pool of service 1 is 50 GB, then the effective allocation limit of service 2 is 42.5 GB. 
This allocation happens because service 1 is already using 50 GB and together they can’t exceed the global allocation limit of 92.5 GB.