topic what is buffering? in Application Development and Automation Discussions

what is buffering?

Former Member — Sat, 18 Nov 2006 07:25:18 GMT

hello experts

1)what is buffering in sap ?

2)which tables can be buffered ?

3)how the buffering of the table techicaly works?

4)what is transperent table /pooled table and cluster table

Thanks

mahya

Re: what is buffering?

Former Member — Sat, 18 Nov 2006 07:30:47 GMT

check following links...

help.sap.com/saphelp_nw04/helpdata/en/cf/21f244446011d189700000e8322d00/content.htm

help.sap.com/saphelp_sm40/helpdata/en/c4/3a6dbb505211d189550000e829fbbd/content.htm

www.sts.tu-harburg.de/teaching/sap_r3/ABAP4/select.htm

Re: what is buffering?

Former Member — Sat, 18 Nov 2006 07:39:56 GMT

Hi ,

Refer this link.

http://www.is-edu.hcmuns.edu.vn/WebLib/Books/Database/0-672-31217-4/ch05/ch05.htm#BufferingaTable

http://www.is-edu.hcmuns.edu.vn/WebLib/Books/Database/0-672-31217-4/index.htm

Regds,

Vinsa.R

Re: what is buffering?

Former Member — Sat, 18 Nov 2006 08:03:17 GMT

1.Buffering a table improves the performance when accessing the data records contained in the table.

The table buffers reside locally on each application server in the system. The data of buffered tables can thus be accessed directly from the buffer of the application server. This avoids the time-consuming process of accessing the database.

2.While creating a table in SE11 in technical settings u have to specify whether the table is to be buffered or not.(only transparent table and pooled table can be buffered).

3.The table buffers lie in shared memory. There is a single-record table buffer TABLP and a generic/full table buffer TABL. The two table buffers differ primarily in how they manage free storage areas and in their displacement mechanisms.

4.A transparent table is a database table which is defined in the ABAP Dictionary and then created in the database.

Cluster table - The data of several cluster tables is stored together in a table cluster in the database. A cluster table is therefore known only in the ABAP Dictionary, not in the database.

Pooled table - The data of several pooled tables is stored together as a table pool in the database. Therefore, a pooled table is known in the ABAP Dictionary, but not in the database.

Re: what is buffering?

Former Member — Sat, 18 Nov 2006 09:29:02 GMT

Whenever an Open SQL statement is used to read a record, the data buffer is checked first to see whether it is there. If not, the data is read from the database. If the table's attributes indicate that the data should be buffered, the record is saved in RAM on the application server in data buffers. Later, if that record is read again, it is read from the buffer instead of the database.

By buffering data, you increase performance in two important ways:

The programs using the buffered data run faster because they don't have to wait for it to come from the database. This reduces delays waiting for the database and the network that connects it.

The other programs that need to access the database run faster because there is less load on the database and less traffic on the network.

Three types of buffering are possible:

Full buffering

Generic buffering

Single-record buffering

Although you use a check box to indicate the buffering type, only one type can be selected at a time. If you choose more than one, an error message will be displayed.

There are two data buffers on each application server, and the buffering type chosen determines which buffer is used. On an application sever there are:

The generic record buffer

The single-record buffer

The generic record buffer is called TABL (short for "table"). The single-record buffer is TABLP ("P"' stands for "partial").

Full Buffering:

To activate the full buffering type, tickmark the Full check box. When an attempt is made to read data from a fully buffered table, the system looks in the TABL buffer for it. If it is not found there, all rows are loaded from the database into TABL . This happens whenever a select statement for it is executed, no matter how many records match the where clause. Even if no records match, all are loaded into the buffer if the table is not already there or if it has been invalidated due to buffer synchronization.

Loading of TABL does not occur with select single statements; only select/ endselect does this. If the table is fully buffered and a select single statement is executed, no records are loaded into TABL. However, if the table is already loaded into TABL, select single will read records from it.

During buffer synchronization, the entire table is invalidated if any record within it changes. The next time data is read the entire table is reloaded.

Full buffering is appropriate for small tables that seldom change.

Generic Buffering:

With generic buffering, a group of records is loaded into TABL instead of the entire table. To activate this type of buffering, tickmark the Generic check box and put a number n in the No. of Key Fields so that the n left-most fields of the primary key will group records. When a record is read and n is 1, all records having the same value in the first field of the primary key are loaded into the buffer. When a record is read and n is 2, all records having the same value in the first two fields of the primary key are loaded into the buffer.

Generic buffering is suitable for tables in which records are usually accessed in sets or groups.

Single Record Buffering:

With this type of buffering, select single picks one record into the single record buffer TABLP. With this buffering type, records are only buffered when the select single statement is executed. Select/endselect does not load or read TABLP.

Single-record buffering is appropriate for very large tables in which a small percentage of the records are read often. For single-record buffering to work, records must be read using the select single statement.

There are two buffers: TABL (the generic record buffer) and TABLP (the single record buffer). There are also two varieties of the select statement: select and select single. The select statement loads TABL and the select single statement loads TABLP.

When reading, select only reads TABL; it ignores TABLP. select single reads both buffers. This behavior is summarized in Figure 5.20. Remember that a record can only be in one buffer at a time because a table can only have one buffering type.

I hope it helps.

Best Regards,

Vibha

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Re: what is buffering?

anversha_s — Sat, 18 Nov 2006 09:58:54 GMT

Hi,

about Buffering:

its a memory area in server to store database values.(master data)

lets assume, you have some master data(in a table)and this data may have accessed by many people everyday. so to display the data to the user everytime system has to go to that table to fetch the values. this fetching is time consuming and increases network traffic. so to avoid this,what we do is,

when ever user requires any data first system will check its available in buffer or not,if not,then it will go to database and will fetch the records and display it to the user .at the same time this data will be added to the buffer for future use.

primarly, buffering concept is used for MASTER data.we can say data which is not changed soo frequently,we use BUFFERING technique for faster response.

Buffering : this helps to reduce the database access from the application server.

All the ,master data tables are buffererd. ie, if we accessed the master data table once for a certain time , it will be buffered in the application server.

so the next time no need to go to the data base server.

this will improve the performance

Regards

Anver

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