Cluster table

[Former Member]

Hi all,

what are the adventage of cluster table/table cluster? I know concept of those.I red SAP lib. i need advantage and usage of cluster table/table cluser.

Thanks

L.Velu

[Former Member]

Cluster tables can be used to strore control data. They can also be used to store temporary data or texts, such as documentation.

[Former Member]

hi,

i'm sending very important links to u for understanding the concepts::

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

another important link

[www.sap-img.com/abap/the-different-types-of-sap-tables.htm]

[web.mit.edu/sapr3/dev/sap_table_types.htm ]

tahnks

if these links work for u

please reward points.

[Former Member]

hi,

Pool tables are defined to host lots of small tables. The reason for them is to reduce the number of tables in the database. In 1992 databases could not handle that number of tables R/3 needed. Even today you see problems due to the high number of tables in SAPs applications. Just watch out for Notes regarding problems with catalog tables or views on an Oracle database. Some of the tables originally placed in Pool tables are later converted to transparent tables, for performance reasons.

Cluster tables where those tables designed for this other restriction you heard from (more than 255 fields). But they have other advantages too. They store information's belonging together in the same database blocks, this improves also performance when you read them

Hope this is helpful, Do reward.

[Former Member]

hi,

Table pools (pools) and table clusters (clusters) are special table types in the ABAP Dictionary. The data from several different tables can be stored together in a table pool or table cluster. Tables assigned to a table pool or table cluster are referred to as pooled tables or cluster tables.

A table pool or table cluster should be used exclusively for storing internal control information (screen sequences, program parameters, temporary data, continuous texts such as documentation). Data of commercial relevance is usually stored in transparent tables.

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

A cluster key consists of a series of freely definable key fields and a field (Pageno) for distinguishing continuation records. A cluster also contains a long field (Vardata) that contains the contents of the data fields of the cluster tables for this key. If the data does not fit into the long field, continuation records are created. Control information on the structure of the data string is still written at the beginning of the Vardata field.

The records of all cluster tables with the same key are stored under one key in the assigned table cluster. The values of the key fields are stored in the corresponding key fields of the table cluster. The values of all data fields of the assigned cluster tables are written as a string to the Vardata field of the table cluster. Besides the actual data values, the data string contains information on the structure of the data and which table it comes from. If the string exceeds the maximum length of the Vardata field, a continuation record is written with the same key values. The continuation records for a key are distinguished by their value in field Pageno. The actual length of the string in the Vardata field is stored in the Pagelg field by the database interface.

You need the structural information stored in the ABAP Dictionary to read the data from a pooled table or cluster table correctly. These tables can therefore only be processed using Open SQL with the cluster interface, and not with Native SQL directly in the database.

cheers,

Hema.

[Former Member]

hi, also chk this.

Table Cluster :

Database table in the database that contains the data of several cluster tables.

Cluster Table :

Database table defined in the ABAP Dictionary, whose version on the database is not only assigned to one table defined in the ABAP Dictionary. Several cluster tables are assigned to a table cluster in the database. The intersection of the key fields of the cluster tables forms the primary key of the table cluster. The other columns of the cluster tables are stored in compressed form in a single column VARDATA of the table cluster. You can access cluster tables only via Open SQL, and only without using joins.

cheers,

Hema.