BW tables unload

[Former Member]

Hi Folks,

We have a question regarding the unload priority for BW on HANA.

Have any of you folks unloaded the DSO tables manually which have a priority set to 5.

Any recommendations regarding the same.

[lucas_oliveira]

Hi ,

If I'm not mistaken unload priority 5 is the stock value for standard DSO active tables and Fact tables from Infocubes. That value is set there to make sure these tables can stay in memory as much as possible.

Obviously, that number alone does not mean anything. If there's a memory shortage HANA will evaluate that number along with the amount of time that you didn't use that table (in fact its columns).

Generally speaking you can unload any CS table from memory (knowing the impacts of doing so). They'll get loaded again as soon as you request columns from it.

Now, I'm not sure why you're going into that direction. Could you please clarify what is the scenario you're going through?

BRs,

Lucas de Oliveira

[Former Member]

Hi Lucas,

Yes you are absolutely correct unload priority is 5 for standard DSO and 7 for write optimised DSO's.

It was a query BW team asked whether they can unload the not used tables.

That was their direction, not sure about the recommendations from SAP on this.

[lucas_oliveira]

Hi,

If your system is properly sized you shouldn't need to unload anything manually/programatically. The DB design would take care of making space on RAM in order to maintain operation smothly.

I've seen cases though, that customers develop ABAP reports to unload data (staging tables mostly) from memory after loading them into the data mart layer. Obviously a *workaround* for an undersized scenario.

BRs,

Lucas de Oliveira

[jgleichmann]

Hi,

by default the HDB automatically unloads unused tables if memory is low. So there is no need to do this manually.

If you have a scenario which the sizing is not adequate, you can adjust this parameters:

Parameter	default	Unit	Header 2
global.ini -> [memoryobjects] -> unused_retention_period	0 (disabled)	s	Number of seconds after which an unused object can be unloaded
global.ini -> [memoryobjects] -> unused_retention_period_check_interval	7200	s	Check frequency for objects exceeding the retention time

Configuring a retention for unloads typically provides no advantage and increases the risk of unnecessary unloads and loads. Therefore these parameters should only be set in exceptional situations.

For more details => 2127458 - FAQ: SAP HANA Loads and Unloads

Regards,

Jens