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How to free-up the Memory in SAP HANA? Prepared by Debajit Banerjee

http://debajitb.wix.com/debajitbanerjee | http://debajitb.wix.com/debajitbanerjee/apps/blog 1

Under normal circumstances, the SAP HANA database manages the loading and unloading of tables into and

from memory independently. Actually, the main aim of SAP HANA database is to keep all relevant data in memory.

But, one can manually load and unload individual tables if necessary. How?

....It’s simple, and it can be done from HANA Studio itself.

Select the table by right click and choose the option “Unload …”

And later, manually load the table into memory again, if needed.

Moreover, if somebody fires the query associated to the same unloaded table, SAP HANA will pick & load the same table

into memory FULL or PARTIALLY, purely depending upon the executed query.

Again, if one needs to free up memory, he/she can manually trigger the delta merge operation for a column table

manually in SAP HANA Studio. The delta merge operation is related to the memory management concept of the column

store, i.e., the part of the SAP HANA Database that manages data organized in columns in memory.

So, options are as follows:

“Unload …” – Free up memory by unloading table from memory

“Load …” – Loading the table into memory

“Merge…” – Triggering delta merge operation for a column table

Here are the screenshots for clear understanding of table unloading from and loading into memory:

In this example, we will unload a table, EKKN from memory and then reloaded into memory.





It actually triggers the equivalent statement ‘SELECT TOP 1000 * FROM “schema_name”.”table_name”’ at the backend.

So, here is the result.

And this triggers the change in the memory also. The same table has been PARTIALLY loaded into memory.



Later, the corresponding table has been FULLY loaded into Memory.

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