Types Of DDIC Table - There are three types of SAP DDIC table that you can define -
1. Transparent Table - 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. For each transparent table definition in the dictionary,
there is one associated table in the database. The database table has the same name, the same number of fields, and the fields have
the same names as the R/3 table definition. They are used to hold application data. Application data is the master data or transaction
data used by an application.
2. Cluster Table - A cluster table is a SAP Proprietry which 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. It holds many
cluster tables. In cluster table, tables have a part of their primary keys in common.
A cluster is adavantages in the case where data is accessed from multiple tables simultaneously and
those tables have at least one of their primary key fields in common. Cluster tables reduce the number
of database reads and therby improve performance.
3. Pooled Table - A pool table is also a SAP Proprietry which has a many-to-one relationship with a table in the database.
For one table in the database, there are many tables in the Data Dictionary. The table in the database has a
different name than the tables in the DDIC, it has a different number of fields, and the fields have
different names as well.
Restrictions on Pooled and Cluster Tables: -
1. Pooled and cluster tables are generally used only by SAP and not used by developers,
due to proprietry format of these tables within the databse and technical
constratints to use within ABAP/4 programs.
2. Secondary Indexes cannot be created on Pooled and Cluster Tables.
3. Can't be use ABAP/4 SQL construct 'Select Distinct' or 'Group By'.
4. Native SQL cannot be used on Pooled and Cluster Tables.
5. Field names cannot be specify after the 'Order By' clause. 'Order By'
with primary key is only allowed.
Note: You can't use a pooled table with a join. In case of Table Pool and Table Cluster, within a technical
setting you can only change SIZE.
Important Note on Pooled Table and Cluster Table
1. For creating pooled table or cluster table you will have to assign the Table pool
or Table cluster in the 'Delivery and Maintainence' tab.
2. You can set technical setting as well like in transparent table.
3. In pooled table, you cannot use indexes and append structure features.
4. In cluster table, you cannot use indexes features but can use append structure.
5. For cluster table you will have to define a key which will match to table cluster
to which it has been assigned.
6. For both pooled table and cluster table it is recommended to use MANDT client
field, but this is not mandatory.
7. Both pooled table or cluster table exist physically in database.
8. To access pooled table or cluster table you can write a direct OPEN SQL query
(Not NATIVE) same as you write for transparent table.
The Differences Between Pooled Table and Cluster Table
1. In pooled table both INDEX and APPEND STRUCTURE is disabled while in
cluster only INDEX is disabled.
2. Cluster table must have one key common but this is not the case for pooled table.
