elementary dictionary types

Former Member — Sat, 23 Feb 2008 03:57:24 GMT

hi experts,

elementary dictionary types ara aslo referred to as what

Re: elementary dictionary types

Former Member — Sat, 23 Feb 2008 04:01:47 GMT

ABAP Dictionary

You can define any user-defined types in the ABAP Dictionary. These can be used in the ABAP program to define data objects and types analogously to types that are predefined in the ABAP program (such as C or I) or types that are defined locally in ABAP programs.

The following type categories can be defined in the ABAP Dictionary:

Data elements (elementary types)

Elementary types have no structure. They describe the data type attributes (such as given Dictionary data type, number of places) and information that is relevant for the screen (such as title) of unstructured data objects (variables/fields).

Structures (structured types)

Structured types describe the structure and functions of any structured data objects, that is of data structures with components of any type.

A component can be a field with an elementary type or can itself be a structure. A table can also be used as a component in a structure.

A database table always has a structure and is therefore implicitly a structured type. However, the fields of a database table can only have an elementary type.

Table types

Table types describe the structure and functions of internal tables in the ABAP program. Their rows can have any row type. Table types with elementary row type therefore can be defined just the same as multi-dimensional table types (table types with a table type as row type) or table types using structures with table-like components.

The options for creating types with structured types and table types can be combined as required. In this way you can define any complex types globally in the ABAP Dictionary and use them in ABAP programs. The runtime object of the Dictionary type (nametab) is the interface for their use in ABAP programs. The runtime object permits very efficient access to the relevant information for the type in compressed form.

The central definition of types that are used more than once in the ABAP Dictionary allows them to be changed centrally. These changes are made at all the relevant locations by the active ABAP Dictionary. For example, ABAP programs adjust to the changed type definitions when they are recreated. When a type is changed, all the objects (e.g. types or tables) that use this type are automatically adjusted to the change at activation.

All Dictionary types lie in a common namespace. A data element, for example, therefore may not have the same name as a structure. However, a type defined in an ABAP program and a Dictionary type may have the same name.

The following shadowing rule is valid when using types in ABAP programs:

If the names are identical, the local types shadow the types of the type groups and the types defined globally in the Dictionary.

Regards.

Re: elementary dictionary types

Former Member — Sat, 23 Feb 2008 04:04:20 GMT

The DDIC is nothing but the ABAP Dictionary. The ABAP Dictionary centrally describes and manages all the data definitions used in the system.

Data types

Data types are the actual type definitions in the ABAP Dictionary. They allow you to define elementary types, reference types, and complex types that are visible globally in the system. The data types of database tables are a subset of all possible types, namely flat structures.

Data Elements

Data elements in the ABAP Dictionary describe individual fields. They are the smallest indivisible units of the complex types described below, and are used to specify the types of columns in the database. Data elements can be elementary types or reference types.

Structures

A structure is a sequence of any other data types from the ABAP Dictionary, that is, data elements, structures, table types, or database tables. When you create a structure in the ABAP Dictionary, each component must have a name and a data type. In an ABAP program, you can use the TYPE addition to refer directly to a structure.

If you define a local data type in a program by referring to a structure as follows:

TYPES <t> TYPE <structure>.

Table Types

Table types are construction blueprints for internal tables that are stored in the ABAP Dictionary.

When you create a table type in the ABAP Dictionary, you specify the line type, access type, and key. The line type can be any data type from the ABAP Dictionary, that is, a data element, a structure, a table type, or the type of a database table. You can also enter a predefined Dictionary type directly as the line type, in the same way that you can with a domain.

Type Groups

Before Release 4.5A, it was not possible to define standalone types in the ABAP Dictionary to which you could refer using a TYPE addition in an ABAP program. It was only possible to refer SAP AG BC - ABAP Programming

Data Types in the ABAP Dictionary to flat structures. Structures in programs corresponded to the structures of database tables or structures in the ABAP Dictionary. In ABAP programs, you could only refer to database tables and structures in the ABAP Dictionary using LIKE. It was, however, possible to refer to individual components of the Dictionary type. Complex local data types such as internal tables or deep structures had no equivalent in the ABAP Dictionary. The solution to this from Release 3.0 onwards was to use type groups. Type groups were based on the include technique, and allowed you to store any type definitions globally in the Dictionary by defining them using TYPES statements.

Views:

There are 4 types views are avilable in SAP.

Database View - To club more than one table

Projection View - To hide fields in one table

Maintanance View - To maintain database records in table

Help View - To provide help for a fields (Same functionality as Search help. This is outdated)

View are improves perfromance in the following aspects

1. If you want to use more than two table in 'JOIN' condition better to use Views . It will improves performance of a program

2. If you want to use mutiple FOR ALL ENTRIES clause, better to club all SELECT statement in a view.

Lock Objects:

Lock objects are use in SAP to avoid the inconsistancy at the time of data is being insert/change into database.

SAP Provide three type of Lock objects.

- Read Lock(Shared Locked)

protects read access to an object. The read lock allows other transactions read access but not write access to

the locked area of the table

- Write Lock(exclusive lock)

protects write access to an object. The write lock allows other transactions neither read nor write access to

the locked area of the table.

- Enhanced write lock (exclusive lock without cumulating)

works like a write lock except that the enhanced write lock also protects from further accesses from the

same transaction.

You can create a lock on a object of SAP thorugh transaction SE11 and enter any meaningful name start with EZ Example EZTEST_LOCK.

Use: you can see in almost all transaction when you are open an object in Change mode SAP could not allow to any other user to open the same object in change mode.

Example: in HR when we are enter a personal number in master data maintainance screen SAP can't allow to any other user to use same personal number for changes.

Technicaly:

When you create a lock object System automatically creat two function module.

1. ENQUEUE_<Lockobject name>. to insert the object in a queue.

2. DEQUEUE_<Lockobject name>. To remove the object is being queued through above FM.

You have to use these function module in your program.

Search Helps:

These are two types.

Elementary n Collective.

1) Elementary search helps describe a search path. The elementary search help must define where the data of the hit list should be read from (selection method), how the exchange of values between the screen template and selection method is implemented (interface of the search help) and how the online input help should be defined (online behavior of the search help).

2) Collective search helps combine several elementary search helps. A collective search help thus can offer several alternative search paths.

3)An elementary search help defines the standard flow of an input help.

4) A collective search help combines several elementary search helps. The user can thus choose one of several alternative search paths with a collective search help.

5)A collective search help comprises several elementary search helps. It combines all the search paths that are meaningful for a field.

6)Both elementary search helps and other search helps can be included in a collective search help. If other collective search helps are contained in a collective search help, they are expanded to the level of the elementary search helps when the input help is called.

See the below link to understand this completely:

http://help.sap.com/saphelp_nw2004s/helpdata/en/cf/21ee93446011d189700000e8322d00/frameset.htm

Rewards if useful.

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elementary dictionary types

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