SAP stores the content in tables (Every data except start and stop logs is stored in DATABASE, no prog/ no data is available in the file system)

There are four types of Buffering
1. FULL Buffering
2. Generic Buffering
3. Single Record Buffering
4. No Buffering

This is maintained for each table SE13 refer USR02 Table.
1. Full Buffering: The tables which are frequently used and rarely modified are eligible for buffering. (Also which are small in size)
Eg: T000 have all the clients and required to create a client copy. (This is fully buffered)

2. Generic Buffering: Tables which are relatively large, frequently used, rarely modified using a set of keys (Fields)
Eg: USR02; T001 Company info

3. Single Record Buffering: The tables which are large in size, frequently used and rarely modified are buffered using a primary key.

4. No Buffering: The tables which are large frequently used, and frequently modified are not eligible for buffering.. VBAK (SALES), EKKO (PURCHASE)

This complete journey should be completed within 600 Milli seconds on an average or goes up to 600 Seconds Max.

1. Front End Time/ GUI Time : Time taken by the user to reach the dispatcher is called as Front end time. The GUI time should not exceed more than 200 M.Sec. If it exceeds this consider the following.

1. User desktop is slow
2. If this is same with all the users, network might be congested.
3. The user request is expensive (FI and basis will logon to the central instance. Rest of all the users are allowed to login to Dialogue instance)
Note: GUI response time is not considered as a part of the Dialogue response time because the request is not received by the dispatcher.

2. Wait Time: The amount of time the user request sits in the queue. Generally it should not be more than 50 M.Sec or 10% of the response time. If the time exceeds, consider the following.

1. The work process are not sufficient to handle the user requests. (1:5)
2. There are sufficient processes but the existing process are held with expensive request.
Login/disable_multi_gui_login. Continue Reading …

SAP systems consists of more than one client – technically 1000 client can be created in one system. So we need to identify which client is the business client. Preciously SAP is client based (A mandatory field while login)
Each client is defined with a logical system name that is defined in SALE. (Sap System linking and enabling). Each system is identified by SID, client by 3 digit number. So, Logical system number should be <SID>CLNT<CLNT_Number>

To identify the systems easily by name
1. Goto > SALE > Basic Settings > Logical System
2. Define Logical System (<SID>CLNT009)
3. Assign logical system to the client.

There should be unique SID in the Landscape.

Defining RFC Connection – SM59
1. SM59 – Provide the name of the logical system
2. Select the connection type ’3′
3. Description about the connection
4. Technical settings (Host name and Instance No)
5. Logon Security (Client, UID, PWD, Logon Language)
6. Save the connection, Test Connection, Remote logon

RFC is used to communicate between SAP systems and SAP to Non-SAP systems using TCP/IP protocol.  RFC’s are defined in [SM59]. There are 4 types of RFC’s

1. Asynchronous RFC
2. Synchronous RFC
3. Transactional RFC
4. Queue RFC

1. Asynchronous RFC – (Like a post card). The sending system may or may not receive it. i.e. there is no acknowledgement from the receiving . The transmission is not reliable.

2. Synchronous RFC – It is not like ARFC. It gets an acknowledgement from the target system. (like a register post).
If the receiving system is not available the process goes into RFC/ CPIC/ Sleep mode and waits until it is wakened by the target system. Target system/ Receiving system may be busy i.e. all the resources are used up. This is reliable but time consuming and expensive (Client Copy) the job should get finished.

Note: SAP uses CPIC protocol SAP specific (Common Programming Interface for Communication) to communicate between system.

3. Transactional RFC – TRFC – It is an advanced version of ARFC and SRFC. The request goes to receiving system if it is not handled a Transaction ID is generated by the source system. A program RSARFCSE is scheduled in the background to run for every 60 seconds. Transaction SM58 is used for Transactional RFC. It is used to document all the transactional ID’s and ensure that they are received by the recipient system. This is consistence and reliable.

4. Queued RFC – It is an advanced version of TRF and ensures that the transaction is committed based on FIFO/ Queue. It ensures transaction consistency of LUW and reliability of data transmission.
SMQ1 – to monitor the outbound queues of a sending system refer SCOTT for FAX…
SMQ2 – Provides interface to monitor Inbound queues.

SMGW is used to monitor the gateway process. Gateway is used to communicate between SAP and NON-SAP systems. There will be only 1 gateway/ instance. If required we can also install a standalone gateway on a JAVA engine.

Gateway listens on port ’3300′+instance number (3300, 3301,3302 where 01, 02 are the instances).

Gateway provides an interface so that the external system can communicate with SAP system on the specified port.

When RFC’s are defined between the systems they use SAP gateway when (ALE, EDI, IDOC are transferring they use gateway)