FEMS Compression

[former_member93815]

In BIA you can now use FEMS compression. What does FEMS stand for and how will the compression improve performance ?

[torsten_wirth]

https://blogs.saphana.com/2013/05/15/bw-on-hana-and-the-fems/

[former_member366279]

Hi,

I could give a bit more detailed explanation about FEMS and FEMS compression.

FEMS expresses the restriction information. Global filter is FEMS 0 and local filter (like in local selection or Restricted Key Figure) is FEMS>0, i.e. 1,2 ,3 ... n

The FEMS of a query could look like this:

FEMS 0000 0COSTCENTER I (include) BT (between) 1000 2000

FEMS 0000 0COUNTRY I EQ (equal) DE

FEMS 0001 0CALMONTH I EQ 201001

FEMS 0002 0CALMONTH I EQ 201002

FEMS 0002 0MATERIAL I EQ AAA

FEMS 0003 0MATERIAL I EQ AAA

...

The intersection of global filter(FEMS=0) and each local filter(FEMS>0) is the restriction that is used to get data from cube.

Now about FEMS compression.

For the data record that is returned from BWA index to BW system, FEMS information is attached to it.

Without FEMS compression, there is only one FEMS that can be attached to data record.

It means that, in case of several FEMS has common data record, it still needs to be returned several times for each FEMS which is not very efficiant.

Now with FEMS compression, several (Maximum 4, I think) FEMS is combined to one big number and attached to the data record.

Then it is only transfered between BWA and BW once thus performance is improved.

Later it gets split again in OLAP processor to get the original FEMS numbers.

For the above example, FEMS 2 and FEMS 3 could have common data.

With FEMS compression, the returned FEMS could looks like 20003 or 2003 or 203 or 23.

The combination of FEMS 39, 128, 6 could look like 39128006.

Regards,

Patricia

[matthias_klocke]

Hi,

please have a look at SAP Note 1074953 u2013 FEMS, BIA Optimization

and the

How To... Plan for, Implement and Maintain SAP NetWeaver BW Accelerator Use Cases

http://www.sdn.sap.com/irj/scn/index?rid=/library/uuid/80297212-f1d7-2b10-9191-c1b6c5dd1c80

section 9.1.

FEMS are FormulaEleMent Selection, however the previous answers name it more precisely and call it Selection Groups. I would call it Finite EleMent Selection.

Regards, Matthias

[former_member93896]

Hello,

Matthias is on the right track. A lot of SAP developers are physicists and mathematicians so I believe FEMS actually refers to Finite Element Solver (http://en.wikipedia.org/wiki/Finite_element_solver). Although the BW OLAP Engine isn't solving partial differential equations, some of our customer's queries certainly come close to it in complexity ;-).

Regards,

Marc

SAP NetWeaver RIG

[premkrishna_natarajan]

Hi,

In OLAP, FEMS denote the restrictions that we provide in a query. In the query definition, if we provide a global restriction, then it is denoted internally in OLAP as Fems 0 for all globally restricted characteristics. If we have some restrictions, say restrict an infoobject for each cell in the output, then those are the Fems 1, 2, ...N restrictions, basically those which are not global restrictions.

~Prem

[former_member93815]

I know you can use FEMS compression with BIA, but I want to know what it actually does and what FEMS means. I haven't found anything so far.

[Former Member]

We can use FEMS Compression ON and this feature is available from TREX REV44 and SAP recommends this one.

Regards

Karthi

[chemicala_srimallikarjuna]

Hi,

pls chk this link

http://help.sap.com/saphelp_nw70/helpdata/EN/f2/c9bae61cca904284aebbecc84ed01b/frameset.htm

Hope this helps,

Regards

CSM Reddy

[Vitaliy-R]

Hi CSM Reddy,

This link says close to nothing about what FEMS is. Could you please elaborate a bit more in your own words?

Much appreciated,

-Vitaliy

[ssurampally]

Hi,

FEMS compression new feature available in BI Accelerator. It reduces the transport costs and eliminates the dulicate records when you execute the query on BIA side. This improves the BI Accelerator perfomance.

To activate this feature in BIA we use TRex Admin tool.

Thanks

Srekanth.

[former_member93815]

I know this already, but I want to know what FEMS means and a clear description of what the compression actually does and how exactly it improves performance.

[Vitaliy-R]

Hi Eduard,

I do not think anyone still knows where FEMS came from. I believe it should be something in German. I looked into OLAP code some time ago, and found FEMS variable there, that stores separate subsets of result set as FEMS1, FEMS2, FEMS3 etc...

I know it doesn't help though. Best would be to get the answer from SAP developers.

Regards,

-Vitaliy