TABLES

[Former Member]

ABAP GURU'S

1- WHAT IS THE ACTUAL DIFFRENCES BETWEEN POOLED AND CLUSTER TABLE.

THANKS

[Former Member]

pls go through this link

http://help.sap.com/saphelp_nw04/helpdata/en/cf/21f083446011d189700000e8322d00/content.htm

<REMOVED BY MODERATOR>

Edited by: Alvaro Tejada Galindo on Apr 11, 2008 4:49 PM

[Former Member]

hi,

1.Transparent Tables

•A transparent table in the dictionary has a one-to-one relationship with a table in the database.

•Its structure in R/3 Data Dictionary corresponds to a single database table.

•Transparent tables are much more common than pooled or cluster tables.

•They are used to hold application data.

• Application data is the master data or transaction data used by an application.

2.Table Pools and Pooled Table

• Pooled table in R/3 has a many-to-one relationship with a table in the database.

• For one table in the database, there are many tables in the R/3 Data Dictionary.

• When you look at a pooled table in R/3, you see a description of a table.

• However, in the database, it is stored along with other pooled tables in a single table called a table pool.

• A table pool is a database table with a special structure that enables the data of many R/3 tables to be stored within it.

• It can only hold pooled tables.

• R/3 uses table pools to hold a large number (tens to thousands) of very small tables (about 10 to 100 rows each).

• Table pools reduce the amount of database resources needed when many small tables have to be open at the same time.

• SAP uses them for system data.

• Pooled tables are primarily used by SAP to hold customizing data.

3.Table Cluster and Cluster Table

• A cluster table is similar to a pooled table.

• It has a many-to-one relationship with a table in the database.

• Many cluster tables are stored in a single table in the database called a table cluster.

• A table cluster is similar to a table pool.

• It holds many tables within it.

• The tables it holds are all cluster tables.

• Like pooled tables, cluster tables are another proprietary SAP construct.

• They are used to hold data from a few (approximately 2 to 10) very large tables.

• They would be used when these tables have a part of their primary keys in common, and if the data in these tables are all accessed simultaneously.

Restrictions on Pooled and Cluster Tables

• Pooled and cluster tables are usually used only by SAP and not used by customers.

• Secondary indexes cannot be created.

• You cannot use the ABAP/4 constructs select distinct or group by.

• You cannot use native SQL.

• You cannot specify field names after the order by clause.

• Order by primary key is the only permitted variation.

<REMOVED BY MODERATOR>

Edited by: Alvaro Tejada Galindo on Apr 11, 2008 4:49 PM

[Former Member]

Hi,

Cluster tables and Pooled tables have many to one relationship with the underlying database.

A table pool corresponds to a table in the database in which all records from the pooled tables assigned to it are stored.

Several logical data records from different cluster tables can be stored together in one physical record in a table cluster.

A pooled table cannot have the name having more than 10 characters.

All the key fields of the pooled table must be of character data type.

In pooled tables, the maximum length of the key field/data fields should not exceed the length of varkey/vardata of the pool respectively.

In cluster table the records having the same key are stored in a single key in the cluster.

If there is an overflow of the data records a continuation record is created with the same table key.

cheers,

Sai.

[Former Member]

Hi Dear.....

................

hi,

Pool Tables (match codes, look up tables)

Should be accessed via primary key or

Should be buffered (SE11->Display Table->technical settings)

No secondary indexes

Select * is Ok because all columns retrieved anyway

Cluster Tables (BSEG,BSEC)

Should be accessed via primary key - very fast retrieval otherwise very slow

No secondary indexes

Select * is Ok because all columns retrieved anyway. Performing an operation on multiple rows is more efficient than single row operations. Therefore you still want to select into an internal table. If many rows are being selected into the internal table, you might still like to retrieve specific columns to cut down on the memory required.

Statistical SQL functions (SUM, AVG, MIN, MAX, etc) not supported

Can not be buffered

Tables Documentation

https://www.sdn.sap.com/irj/sdn/go/portal/prtroot/docs/library/uuid/25c1f5d1-0901-0010-d495-e96d02a0...

1. Table pool is used for storing large number of unrelated logical tables in one physical table. Table cluster is used for storing small number of related logical tables in one physical table.

2. Tables in a cluster must have a significant part of the key common, but tables in a table pool do not have that restriction.

3. One record of a table pool represent one record of any one of the pooled table whereas one record of table cluster represent data from one or more records of all cluster tables (If it fits in one page).

Cluster table contains large amount of data.

This cluster table in database is stored as the combination two or more small database tables.

For example BSEG is a cluster table..

You can find all the Fields of this table in different small tables BSIS, BSAS etc...

The following are the table types used in SAP :

I. Transparent tables (BKPF, VBAK, VBAP, KNA1, COEP)

Allows secondary indexes (SE11->Display Table->Indexes)

Can be buffered (SE11->Display Table->technical settings) Heavily updated tables should not be buffered.

II. Pool Tables (match codes, look up tables)

Should be accessed via primary key or

Should be buffered (SE11->Display Table->technical settings)

No secondary indexes

Select * is Ok because all columns retrieved anyway

III. Cluster Tables (BSEG,BSEC)

Should be accessed via primary key - very fast retrieval otherwise very slow

No secondary indexes

Select * is Ok because all columns retrieved anyway. Performing an operation on multiple rows is more efficient than single row operations. Therefore you still want to select into an internal table. If many rows are being selected into the internal table, you might still like to retrieve specific columns to cut down on the memory required.

Statistical SQL functions (SUM, AVG, MIN, MAX, etc) not supported

Can not be buffered

regards

Sudarsan

[Former Member]

Hi,

Pooled table

Pooled tables can be used to store control data (e.g. screen sequences, program parameters or temporary data). Several pooled tables can be combined to form a table pool. The table pool corresponds to a physical table on the database in which all the records of the allocated pooled tables are stored.

Cluster table

Cluster tables contain continuous text, for example documentation. Several cluster tables can be combined to form a table cluster. Several logical lines of different tables are combined to form a physical record in this table category. This permits object-by-object storage or object-by-object access. In order to combine tables in clusters, at least part of the keys must agree. Several cluster tables are stored in

one corresponding table on the database.

Pool Tables (match codes, look up tables)

Should be accessed via primary key or Should be buffered (SE11->Display Table->technical settings)

No secondary indexes

Select * is Ok because all columns retrieved anyway

Cluster Tables (BSEG,BSEC)

Should be accessed via primary key - very fast retrieval otherwise very slow

No secondary indexes

Select * is Ok because all columns retrieved anyway. Performing an operation on multiple rows is more efficient than single row operations. Therefore you still want to select into an internal table. If many rows are being selected into the internal table, you might still like to retrieve specific columns to cut down on the memory required.

Statistical SQL functions (SUM, AVG, MIN, MAX, etc) not supported

Can not be buffered.