What's behind the EARLY UNLOAD of the Non-active data concept for BW on SAP HANA DB ?

[Former Member]

Hi,

with

SAP Note 1767880 - Non-active data concept for BW on SAP HANA DB

the HOW WARM COLD concept is introduced.

What's behind the EARLY UNLOAD of this note / concept ?

Is it the ALTER TABLE SQL Option UNLOAD PRIORITY  / PRELOAD and setting the flags

of the Dictionnary ViewsC M_CS_TABLES.UNLOAD_PRIORITY ,M_CS_TABLES.IS_PRELOAD ?

Thank You !

Best Martin

[Former Member]

Hi Lars,

how does the unload work in more detail:

-How is the overall memory to be availabe for column tables identified ?

-Which components of M_SERVICE_COMPONENT_MEM contribute to the Column Store ?

-Is there a thtreshold when an unload occures  and how is this defined (which parameter ) ?

-Are the tables, designated to be unloaded somehow marked - can these col tables

be indentfied ?

Thank You

Martin

Message was edited by: Sautter Martin

[lbreddemann]

Hello Martin,

columnstore tables can have an attribute UNLOAD PRIORITY.

This can be checked upon in system view TABLES.

It's a integer value between 0 and 9. 0 means the table won't be unloaded, 9 means if any column/table need to be unloaded at all, this one will be unloaded as early as possible.

In general the parameter is just a weighting factor that puts the tables up or down in the queue of unload candidates.

Concerning the other memory management questions please check http://www.saphana.com/docs/DOC-2299 and the current SPS 6 documentation available on http://help.sap.com/hana_appliance.

Concerning the question on M_SERVICE_COMPONENT_MEM take a wild guess...

select * from m_service_component_memory

HOST	PORT	COMPONENT	USED_MEMORY_SIZE
ld9506	30.003	Column Store Tables	105.102.530.445
ld9506	30.003	Other Engine Components (misc.)	37.960.227.431
ld9506	30.003	Row store tables + Indexes	22.458.706.522
ld9506	30.003	Persistence	1.517.751.936
ld9506	30.003	Database Kernel Statistics and Merge Statistics	1.401.040.576
ld9506	30.003	Auxiliary Row Store Components	1.364.478.483
ld9506	30.003	Memory Management Information	1.245.708.288
ld9506	30.003	Prepared Statement Cache	612.071.568
ld9506	30.003	Kernel Datastructures (Stack-Allocated)	608.739.328
ld9506	30.003	Transaction Management	200.988.992
ld9506	30.003	Column Store Intermediate Results and Shared Datastructures	751.304
ld9506	30.004	Other Engine Components (misc.)	449.819.603
ld9506	30.004	Auxiliary Row Store Components	113.882.464
ld9506	30.004	Kernel Datastructures (Stack-Allocated)	92.626.944
ld9506	30.004	Memory Management Information	62.914.560
ld9506	30.004	Database Kernel Statistics and Merge Statistics	58.092.528
ld9506	30.004	Persistence	48.566.296
ld9506	30.004	Column Store Tables	19.990.496
ld9506	30.004	Prepared Statement Cache	13.869.000
ld9506	30.004	Row store tables + Indexes	6.912.064
ld9506	30.004	Transaction Management	1.831.976
ld9506	30.004	Column Store Intermediate Results and Shared Datastructures	1.264
ld9506	30.005	Other Engine Components (misc.)	1.135.776.855
ld9506	30.005	Column Store Tables	987.949.703
ld9506	30.005	Kernel Datastructures (Stack-Allocated)	278.474.752
...	...

- Lars

[lbreddemann]

Hi Martin,

it's the UNLOAD PRIORITY option.

PRELOAD is a completely different and non-related feature.

The idea for UNLOAD PRIORITY is to let SAP HANA know what tables should be preferred when unloading data from memory.

You can also review the setting taken for the BW objects on SAP HANA level in the storage settings (SE11 -> SE14).

- Lars