Buffers

Former Member — Wed, 23 Jan 2008 13:57:23 GMT

1.What are the buffers available in SAP?List them and explain

2.How many header lines can be created in ABAP/4 for a program?

Re: Buffers

Former Member — Wed, 23 Jan 2008 14:00:46 GMT

good

Each SAP instance (application server) has its own buffers. These buffers are also known as client caches because they are implemented on the client, that is, the application server. SAP buffers occupy memory areas that are local to the work process, and in individual shared memory segments that can be accessed by all work processes. These memory areas are executed for the application server.

check this link,hope this would help you to solve your problem.

http://help.sap.com/saphelp_nw04s/helpdata/en/c4/3a6dbb505211d189550000e829fbbd/content.htm

thanks

mrutyun^

Re: Buffers

Former Member — Wed, 23 Jan 2008 14:01:18 GMT

Hi,

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.

Regards,

Satish

topic Re: Buffers in Application Development and Automation Discussions

Buffers

Re: Buffers

Re: Buffers