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Thursday, 11 December 2014

RFC in SAP - Remote Function Call

RFC in SAP - Remote Function Call


RFC (Remote Function Call)

For business applications, it is necessary to communicate and exchange information (in pre-defined formats) with other systems.Hence, there are well defined mechanisms to enable this communication. SAP has also provided us with such mechanism called RFC, which stands for 'Remote Function Call'.



Mainly 5 Type of RFC,                                                                                                                          
1) Synchronous RFC
2) Asynchronous RFC
3) Transnational
4) Queued

Synchronous RFC : Requires both the systems (client and server) to be available at the time of communication or data transfer. It is the most common type and is required when result is required immediately after the execution of sRFC.

 Asynchronous RFC : It is communication between systems where acknowledgements are not required (it is similar to post card delivery).It doesn't require both the systems to be available at the time of execution and the result is not immediately required to be sent back to calling system.

 Transnational : Transactional RFC is an asynchronous communication method that executes the called function module in the RFC server only once, even if the data is sent multiple times due to some network issue. The remote system need not be available at the time when the RFC client program is executing a tRFC. The tRFC component stores the called RFC function, together with the corresponding data, in the SAP database under a unique transaction ID (TID). tRFC is similar to aRFC as it does not wait at the target system (Similar to a registered post). If the system is not available, it will write the Data into aRFC Tables with a transaction ID (SM58) which is picked by the scheduler RSARFCSE (which runs for every 60 seconds).

 Queued : Queued RFC is an extension of tRFC. It also ensures that individual steps are processed in sequence.To guarantee that multiple LUWs (Logical Unit of Work/ Transaction) are processed in the order specified by the application. tRFC can be serialized using queues (inbound and outbound queues). Hence the name queued RFC (qRFC).
Creating RFC connection                                                                                                                       
SM59 is using to Create RFC connection,

Click on the *Create option                                                                                                                     



Type a name for the RFC Destination and select connection type , different type of connections are there. we are using connection type 3 (ABAP Connection). after it click *Connection test option in the screen.                                                                                                                                             



In technical settings tab select a option IP or Host Name and type in *Target Host and type the          *Instance No. and go to next tab Logon and Security                                                                                                        

Fill the details of the target system to logon                                                                                         
   After that click *Connection test option,        

If it like the above image, the connection test is fine go back and click on *Remote login option    


Click *Start SAP Easy Access to logon target system                                                                   


Now you are the Target system session.                                                                                          

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Monday, 8 December 2014

SAP Buffer

SAP Buffer
THERE R 3 TYPES OF BUFFERING FOR A TABLE:-

1. Full table buffering :- here entire database table buffered to application server.

So further access to same table can be access from application server so, which interm reduces database traffic.

Fullbuffering can only applies to tables which have less data and rarely changed.

Ex-tcodes, company master data like T100, etc

2.Single record buffering:- here only one record can buffered to application server by select single…………… with where all key fields can be specified .

Here if no record exists then also no record information stored to application.

Here it applies to database table which is larger in size and modified frequently.



3. Generic buffering:- here few database table records which matches  can buffered to application server depends on generic keyfields(key fields specified while setting buffer settings).

So further access to same table can be access from application server so, which inters reduces database traffic.

Full buffering can only applies to tables which have less data and rarely changed.

Ex-tcodes, company master data like T100, etc
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SAP Memory Management

SAP Memory Management



=====================================================================
SAP Memory Management
=====================================================================
Virtual memory
All operating systems (supported by SAP) support virtual memory technology. A process allocates virtual memory using logical (virtual) addresses. Each process has its own virtual address space. Virtual memory is fully independent of the physical main memory.
Address space
On 32 bit platforms a virtual address can have values between 0 and 2^32-1, which restricts the sizes to 4GB. As areas of the virtual address space are reserved, this leaves about 2GB available on most platforms. This is not a problem for large SAP systems.

Memory allocation
Allocating memory for a process consists of the following steps:

  1.  Reservation of a segment in the physical memory.
  2.  Linking the physical memory segment to the virtual address space of the process, which means reserving a segment of the same size in the virtual address space and mapping the virtual addresses to physical addresses.
Local process memory

The operating system differentiates between local process memory and shared memory. For local process memory the operating system keeps both allocation steps transparent. Using an API virtual memory only is requested; the operating system does the other tasks, such as reserving physical memory, loading and unloading virtual memory into and out of the main memory.
Shared Memory

If several processes are to access the same memory area, both allocation steps are not transparent.
One object is created that represents the physical memory and can be used by various processes. The processes can map the object fully or partially into the address space. The way this is done varies from platform to platform. Memory mapped files, unnamed mapped files, and shared memory are used.
SAP Paging

Allocation of memory for the current internal session by transferring pages out of memory, similarly to operating system paging.
 
=========================================================================
Functions of the SAP Memory Management
========================================================================
An application runs in an SAP work process where an ABAP program is normally executed. The process requires memory to do this, which is allocated to the process by the memory management system. The order in which the work process is assigned the memory type depends on the work process type, either dialog or non-dialog (see SAP Memory Types), and the underlying operating system.

This is described in more detail in the documentation on the operating system.

The location of the various memory areas in the virtual address space is explained in Virtual Address Space of a Work Process.

The area of a user context that is directly accessible is now extended as needed, if the user context has expanded. For dialog work processes, the data of the user context, including internal tables is located in this expanded area.





Whenever a dialog step is executed, a roll action occurs between the roll buffer in the shared memory and the memory area, which is allocated according to ztta/roll_first in a dialog process. Then the area in the shared memory is accessed that belongs to this user context.
The following graphic displays the roll process performed by the dispatcher.
●  Roll-in cross-user data is rolled in from the common resource in the work process (and is processed there).
●  Roll-out: User-specific data is rolled out from the work process in the common resource (after the dialog step has ended).


=====================================================================
Profile Parameters of Memory Management 
=====================================================================
 Memory Management Resources for One Work Process
ztta/roll_extension: Limit for Extended Memory
ztta/roll_extension_dia: EM Quota for Dialog Work Processes
ztta/roll_extension_nondia: EM Quota for Non-Dialog Work Processes
abap/heap_area_dia: Heap Memory Limit for Dialog Work Processes
abap/heap_area_nondia: Heap Memory Limit for Non-Dialog Work Processes
abap/heap_area_total: Total Quota for Heap Memory
ztta/roll_area: Roll Area
ztta/roll_first: Size of the Initial Allocation from the Roll Area


Memory Management Limitations
abap/heap_area_total: Heap Memory Limit
em/initial_size_MB: Extended Memory Pool Size
rdisp/ROLL_SHM: Roll Buffer Size
rdisp/ROLL_MAXFS: Maximum Roll File Size
rdisp/PG_SHM: Size of the Paging Buffer
rdisp/PG_MAXFS: Maximum Size of SAP Paging File
em/blocksize_KB: Segment Size for the Extended Memory
Memory Management Statistics
em/stat_log_size_MB: Statistics - User Context Size
em/stat_log_timeout: Statistics - User Context Size
Parameters for controlling the Release of SAP Memory for the Operating System
es/disclaim_threshold_MB
es/disclaim_coasting_time_alloc
es/disclaim_coasting_time_free
es/blockdisclaimsize_KB
es/freelist_compactor

Operating system decides where the extended memory resides...
When an instance startup a part of memory allocated to instance called as shared memory.
Which consist of all the buffers, roll area, extended memory etc.
Whenever the user process any tcode work process alloacate to user. Data processed by the work process is stored in two memory areas
1. Roll Area: In which user context data is stored like authorizations, internal table etc.
2. Paging Area : Stores the application program data more precisely abap command including Extract, Import to memory, Export to memory call transaction etc.
Paging Area= Page Buffer + Page File
Page buffer is a part of shared memory where as Page File resides at physical level.
Data swap as per the requirement in Page Buffer and Page File.
If data processing demands more memory, than the concept of Heap came into picture which is also called as local memory.
Memory Parameters are there to defines the values for all of them. If memory utilization for individual work process reached the max. limit of heap than work process stuck in PRIV mode with all the allocated memory.


For more information visit:-

http://levelx.me/blog/wp-content/uploads/2010/11/SAP-Memory-Management-Collection-by-st4rcH1LD.pdf

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