Relation between LIVE CACHE and DATABASE

[lalit_behere]

Hi Gurus,

1. Please provide me the information regarding Live Cache and Database.
Is it analogous to ROM ( Database) and RAM (Live Cache) in computer system.

2. How is the relation maintained between the live cache and the Info Cubes/ DSOs  ?

Regards

Lalit

[former_member458819 · Accepted solution]

Hi

liveCache is one of the database used in APO system.

APO system has 2 database APODB and liveCache.

Generally master data and some other data are stored in APODB.

And some part of transaction data (most of the part) are stored

in liveCache.

For APODB, you can use normal DB like Oracle, MSSQL, DB2, MAXDB.

For liveCache, their is no choice. (liveCache is one of the function

of MAXDB).

From new SCM release, you can use MAXDB for APODB and liveCache.

(But still there is 2 kinds of DB).

If you have DB knowlege, maybe you can get rough image of liveCache.

(Compared to normal DB, liveCache has more bigger datacache. So

all data can be stored in dataCache. <Off course this require

certain amount physical memory>).

Since most of the data are stored in dataCache (it is better to be

stored in datacache. Otherwise expensive disk access occur), APO

application can access data speedly.

(liveCache data is accessed by special routins that are called

from function module start with /sapapo/OM*)

liveCache is often called memory based database. But actually it also

has DB (disk). So same as other DB, DB(disk) has all data. And

its copy is stored in dataCache (memory). The difference between

other DB and liveCache is, it is recommended to store all the data

in dataCache in liveCache, and if most of the data is stored in

liveCache, this means data is on memory. Therefore liveCache is

called memory based database.

About the connection between R/3.

The data exchange between R/3 and APO is done by qRFC.

This interface is called CIF.

So if someone create data in APO, transaction data is stored in

liveCache. As well, this creation also create some even to create

qRFC data to R/3. So this created data is sent to R/3 and stored in

R/3 database. Then this data comes back with R/3 document number to APO

with qRFC format. Then when it arrive in APO, qRFC is executed

and within this function module, APODB and liveCache is accessed

via several function modules including /SAPAPO/OM*.

So if you use SCM system, you have to be careful to the consistency

between APO and R/3 (this consistency check can be done by delta report)

and APODB - liveCache. (Since some of the data are stored in APODB and

liveCache, and there is some relatation between APODB and liveCache)

I hope this explanation help you

Sunil

[Former Member]

Lalit,

"Livecache" is an SAP application in which data is stored and managed.  The livecache routines which access the database are mostly written in C++.  Livecache usually runs on a standalone server (but this is not technically required).

In the past, Livecache routines ran only over a DB kernal called MAXdb, similarly to the way other SAP applications run over, say, Oracle DBMS or MS SQL Server DBMS.  I understand that SAP now intends to migrate LC to run over HANA, but I know very little about this change.

The thing that makes Livecache unique from most other SAP applications is that it is designed and optimized to store and manage the data in memory, rather than on disc.  Since memory access is faster than disc access, use of Livecache allows significant improvements in processing times for data storage and data retrieval functions.  Memory is analogous to RandomAccessMemory (RAM) on a PC, disc is analogous to a hard drive on a PC.  Your question about ReadOnlyMemory is puzzling, ROM is typically used to store static data (but there are exceptions!).  One usually doesn't think of ROM as part of storage for a database application solution.

BW data structures generally are stored on disc.  When it is necessary to move data from BW to LC, or Vice Versa, SAP uses the C++ routines that are part of the LC application.  A common example at the application level would be copying data between Infocubes (disc) and Planning Areas (LC).

http://help.sap.com/saphelp_scm700_ehp02/helpdata/EN/f3/3edeb38ab14f9798d2a800b2c439c9/content.htm?f...

Best Regards,

DB49