Hi,
1.CLIENT is the highest heriarchial unit in any Module in SAP.
In the development business SAP landscape will be divided into 3 systems namely DEVELOPMENT, Testing or Quality and Production.
These are 3 sepearate servers(boxes). they may exist seperately (in 3 system landscape)or sometimes both the DEV and TEST systems together and PRD sepearte(2 type landscape).
This is purely a basis work.
Again coming to each System, there may be different clients in DEV system, as we need diffferent systems to work, one for customizing work, and other for sandbox work and other for Development work(transports), based on the requirements we can define any number of clients.
in PRD there won't be different clients.
Somes times in Quality may exits 2 or 3 clients.
So the requests will be created in DEV in one client and they are released and sent to other systems like QUALITY and PRD once they are perfect.
A single R/3 System can manage the application data for several separate areas of a business (for example, branches). Each of these commercially separate areas in the R/3 System is called a client, and has a number. When a user logs onto an R/3 System, they specify a client. The first column in the structure of every database table containing application data is the client field (MANDT, from the German word for client). It is also the first field of the table key. Only universal system tables are client-independent, and do not contain a client name.
By default, Open SQL statements use automatic client handling. Statements that access client-dependent application tables only use the data from the current client. You cannot specify a condition for the client field in the WHERE clause of an Open SQL statement. If you do so, the system will either return an error during the syntax check or a runtime error will occur. You cannot overwrite the MANDT field of a database using Open SQL statements. If you specify a different client in a work area, the ABAP runtime environment automatically overwrites it with the current one before processing the Open SQL statement further.
Should you need to specify the client specifically in an Open SQL statement, use the addition
... CLIENT SPECIFIED ....
directly after the name of the database table. This addition disables the automatic client handling and you can use the field MANDT both in the WHERE clause and in a table work area.
Reading data
Client Handling
As already mentioned, you can switch off the automatic client handling in Open SQL statements using a special addition. In the SELECT statement, the addition comes after the options in the FROM clause:
SELECT... FROM <tables> CLIENT SPECIFIED. ..
If you use this addition, you can then address the client fields in the individual clauses of the SELECT statement
these links helps u
http://help.sap.com/saphelp_46c/helpdata/en/90/174b6e5733d1118b3f0060b03ca329/frameset.htm
http://help.sap.com/saphelp_46c/helpdata/en/42/0a8a885c2811d2b414006094b9ea64/frameset.htm
Client dependent Means if you create that data in one client is limited to that client only and it is not accessable in other clients
Like SAP SCRIPTS and STD texts data
where as Client Independent means the data if you create in one client that is available in that as well as in other clients
Like All dictionary Objects data and Repository objects data like Programs, Fun modules, tables etc
2.Buffering:
We have 3 types of buffering
There are the following types of buffering:
o single-record buffering
o generic area buffering
o full buffering
Single-record buffering should be selected when :
o For large tables where there are frequent single-record accesses (using SELECT SINGLE ...). The size of the records being accessed should be between 100-200 KB.
o For comparatively small tables for which the access range is large, it is normally advisable to opt for full buffering. Only one database access is required to load such a table for full buffering,
while single-record buffering calls for a very large number of table accesses.
And also check this matter.
Single-record buffering: Only the records of a table that are really accessed are loaded into the buffer
Single-record buffering should be used particularly for large tables where only a few records are accessed with SELECT SINGLE. The size of the records being accessed should be between 100 and 200 KB.
Full buffering is usually more suitable for smaller tables that are accessed frequently. This is because only one database access is necessary to load such a table with full buffering, whereas several database accesses are necessary for single-record buffering.
Check this link :
http://help.sap.com/saphelp_nw04/helpdata/en/f7/e4c5a8a84a11d194eb00a0c929b3c3/content.htm
Cheers,
vasavi.
kindly reward if helpful.
Bluesky
