What is a cluster Table?

Yaopipi
What is a cluster Table? What is the difference with a transparent table?

Xjq

A cluster Table means that many tables are merged into a table. I can find some descriptions in help.
Table Clusters
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 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. A table cluster has the following structure:
Field      Data Type        Meaning
Clkey1      *           First key field
Clkey2      *           Second key field
...
...
...
Clkeyn      *           Nth key field
Pageno     Int2 (5)      Number of the continuation record
Timestamp  Char (14)     Time Stamps
Pagelg     Int2 (5)      Length of the string in vardata
Vardata    Raw (N)      Contains the entries from the data fields of the assigned cluster tables as a string, Max. length N depends on the database system used
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
Database.

Xjq

You can only talk about it. :)
To be honest, I really don't know. My general understanding is that he put different cluster tables in a table cluster, and the structure of this table cluster is composed of the above fields, the key field exists in the corresponding key field, and all other content has the vardata field. In this field, not only the data is stored but also the data is stored in those tables, if this field is exceeded, another record will be written continuously. The pageno field indicates that this is a continuous record. This is the case. I don't know why cluster Table is used.

Nico

   Yaopipi:
       In fact, Xu has already made it clear to you. I think you may need to know a database
   Storage problems. I don't know if you are familiar with Oracle databases, but I can only assume that you are
   Solved :)
       Physically, the data in the database is stored on the disk in the form of data files.
   The format of the data file must be consistent with the disk format of the OS. Because databases often require
   To be used on many different operating systems, there are many physical formats. Logically
   How does the data meet the requirements of diversified storage formats? A simple solution to this problem
   The solution is to use "clusters. In the transparent table, multiple fields of a record are placed in different
   In physical fields, this is troublesome and economic. We can define a vardata super
   Field stores all fields of this record in this field. Read
   Required data. This is the cluster table.
       For example, bseg In the fi module adopts this method. Dataset used in r/3
   This technology is also used. If you use the C language to read the database, you often need to define pointers.
       Well, let's talk about that. If you have any questions, please continue.
Snowwolf

Some big tables in SAP use the same primary key fields at the same time and place the same fields in a table. This new table is called a cluster Table, which generates many cluster tables, is it useful to manage and save resources easily.
Sonicme

Hi all experts,
You have recently studied cluster table. I don't dare to exclusively share it with you.
In fact, there are three types of tables in SAP:
Tranparent table
Pools
Cluster table
The transparent table is consistent with the table concept in various databases.
The table structures specific to sap are pools and cluster tables. They are no longer common tables of various databases and cannot be directly accessed by databases. You can only use your own sap tools for direct access.
Cluster table compresses the data volume.
In definition, the reply of the total bamboo xjq and the reply of the Nico are clear.
Thank you for your valuable experience!
Soncime:)
Sonicme@msn.com
12.08.2002

2002-12-9 19: 25 sczy

Haha, I copied the information in the ABAP database here !!!
The SAP system contains the following list types:
Transparent table
Each transparent table has a corresponding physical table in the database. Physical table name and logical table in Data Dictionary
The name of the definition is consistent. All transactions and application data are stored in transparent tables.
Structure
The structure does not have any data records in the database. Structure is used to define interfaces between programs or between programs and screens.
Additional Structure
A subset of the additional structure definition field, which belongs to another table or structure, but is used as a single
Unique object.
Storage table
Storage tables can be used to store control data (such as screen sequence, program parameters, or temporary data ). Several Storage
Table store can be combined into a table database. This table library is consistent with a physical table library in the database. It contains groups
All records assigned to the database.
Cluster table
Continuous text, such as documents, can be stored in cluster tables. Several cluster tables can be combined into a table cluster. For this
Table type. Several logical rows in different tables are combined into one physical record. This allows an object to be connected to
To store or access tables in a cluster, at least a portion of the keywords MUST match. Several
The cluster Table is stored in a corresponding table in the database.
Create View Structure
The structure of the view generated during the activity. This structure is used as an interface in the runtime environment. Normally not displayed in AB
AP/4 dictionary.

Mampm

As far as I know, there are at least two functions:
1. Store binary data
2. Data security: only the corresponding content can be read through the program, which facilitates permission control.
Yaopipi

Right. The key is to find the primary key.
Knightsun

There are three types of tables in R/3:
Transparent table
Share a table
Cluster table
Transparent table:
   Transparent tables correspond to tables in the database one by one, with the same table name, number of fields, and field name. Definitions of transparent tables in the ABAP dictionary are independent of those in the database, the defined table has the same structure as the table in the database. When the table is activated, the physical table in the database is stored in the ABAP dictionary.
Share table:
  A shared table has a many-to-one relationship with a table in a database. The table names are different, the number of fields is different, and the field names are different. A shared table is a concept specific to sap. In the database, all the shared tables are stored in one table, which is called 'table pool )'. SAP uses the shared table store system data.
Cluster table:
  The cluster Table is similar to the shared table. It is also a multi-to-one relationship. Most cluster tables are stored in a table named table cluster. Cluster tables are used when some tables share PK or data is accessed synchronously.
The above is my excerpt from a Chinese document for your reference only!
Netzilla

The cluster Table itself is a transparent table. As you can see in SE11, the application that I use to access many cluster tables is used to save internal tables or some structures. Let's simply put, some data objects are defined in a standard way, such as contract pulling. We define transparent tables for storage. However, there are many program internal tables and structures or whatever, which are greatly changed, if you want to save it, you can never define a transparent for each
Table, so you only need to define a unique key (this is very important), and then store the data objects in the cluster table in one brain, OK, you need to use the same key when accessing the cluster table. It is worth noting that you need to understand the definition of the unique key when using the cluster Table, and generally there is a corresponding macro for access.
Nomad

Hoho: The HR staff are familiar with the cluster table. All the time evaluation results and payroll run results are stored in the cluster table.
In general, cluster Table stores a pile of data in a "very large" field in sequence according to certain rules, in the future, read data according to this specific rule.
Improve performance, save space, and enhance security. This is the purpose of cluster table.

Cbwan542399

Cluster table
 You can check the database book. The difference between it and the transparent table is handled for a group of tables,
There is no difference between a single table and a transparent table, but multiple tables form a cluster table and they are physically stored only once for the primary key, therefore, the associated query of the cluster Table can greatly improve the access speed.

04-06-11 21: 41Www.itpub.net
Transparent tables can be connected for queries. Cluster tables can only be queried through simple select queries, such as bseg.
Internal tables are equivalent to arrays and can be queried through loop and read.
The records in the internal table are all edited and viewed in the workspace. The structure is the same as that of the internal table.