SAP HANA Main Memory Sizing is divided into static and the dynamic RAM requirement.
Static RAM Requirement:
The static RAM requirements relates to the amount of main memory that is used for the holding the table data.
Static memory sizing of HANA is determined by the amount of data that is to be stored in memory.
Dynamic RAM Requirement:
Additional main memory is required for objects that are created dynamically when new data is loaded or queries are executed. Since SAP recommends reserving as much memory for dynamic objects as for static ones, for calculating the total RAM the static RAM is multiplied by two.
Steps to Calculate RAM Size:
1.Calculate Uncompressed Data Volume to be loaded in HANA - Source Data Footprint:
Determine the information that has to be transferred (either by replication or extraction) to the SAP HANA database. Note that typically customers will only select a sub-set of information from their ERP or CRM database, so this has to be done at the table level.
The sizing methodology is based on uncompressed source data size, so in case compression is used in the source database, this has to be taken into account as well.
The information required for this step can be acquired with database tools. SAP Note 1514966
contains a script supporting this process for several database systems, for example, DB2 LUW and Oracle.
The current size of all the tables (without DB indexes) storing the required information in the source database is called Source Data Footprint
2.Compression Factor in HANA
In HANA as a side-by-side scenario, the expected compression was 1:5. Through new compression mechanisms the compression ratio increased to 1:7.
There are, however, also significantly higher values, so customers are circulating examples where a factor has been achieved of over 1:50
The compression ratio achieved by SAP HANA can vary depending on the data distribution.
3.Calculation of Static RAM Size
Static RAM Size means the amount of RAM required to store the data in the SAP HANA database.
Assuming the compression factor as 7:
4.Calculation of Dynamic RAM Size
Dynamic RAM is for additional main memory required for objects that are created dynamically when new data is loaded or queries are executed. SAP recommends to keep Dynamic RAM size same as Static RAM size.
5.Calculation of Total RAM Size
The total amount of RAM should be rounded up to the next T-shirt configuration size. For example, if total RAM size is 400 GB, then T-shirt size of M should be selected.